diff --git a/src/app/editor.js b/src/app/editor.js
index 8d4ab5a..aec35ca 100644
--- a/src/app/editor.js
+++ b/src/app/editor.js
@@ -292,6 +292,8 @@ export default class Editor {
 		} else {
 			this.rteEditor.setData( this.markdownEditor.getData() );
 		}
+
+		this.fire( 'sync' );
 	}
 
 	/**
@@ -467,6 +469,15 @@ export default class Editor {
 			} );
 		}
 
+		// Unlock the form whenever the textarea gets sync'ed.
+		{
+			this.on( 'sync', () => {
+				if ( this.getMode() === Editor.modes.RTE ) {
+					unlockForm( this );
+				}
+			} );
+		}
+
 		listenToData();
 
 		/**
@@ -504,9 +515,10 @@ export default class Editor {
 		 */
 		function unlockForm() {
 			if ( textarea.hasAttribute( 'data-github-writer-was-required' ) ) {
-				textarea.required = textarea.getAttribute( 'data-github-writer-was-required' );
+				textarea.required = ( textarea.getAttribute( 'data-github-writer-was-required' ) === 'true' );
 				textarea.removeAttribute( 'data-github-writer-was-required' );
 			}
+
 			textarea.setCustomValidity( '' );
 
 			// Restore the "formnovalidate" attribute on submit buttons.
@@ -529,9 +541,6 @@ export default class Editor {
 			if ( editor.getMode() === Editor.modes.RTE ) {
 				editor.syncEditors();
 			}
-
-			// Since the textarea is sync`ed, the form is good to go.
-			unlockForm( editor );
 		}
 
 		/**
@@ -660,15 +669,16 @@ export default class Editor {
 			const textarea = this.markdownEditor.dom.textarea;
 			const form = textarea.form;
 
-			form.querySelectorAll( '[required]' ).forEach( element => {
+			disabled = Array.from( form.querySelectorAll( '[required]' ) ).some( element => {
+				// Instead of checking the markdown textarea, we check the RTE editor.
 				if ( element === textarea ) {
-					// Instead of checking the markdown textarea, we check the RTE editor.
-					disabled = disabled || ckeditor.isEmpty;
+					// We may have changed the "required" attribute of the textarea. We want the original value.
+					const required = textarea.getAttribute( 'data-github-writer-was-required' ) !== 'false';
+
+					return required && ckeditor.isEmpty;
 				} else if ( !isWiki ) {
 					// For other elements, we just use DOM checks.
-					if ( !element.checkValidity() ) {
-						disabled = true;
-					}
+					return !element.checkValidity();
 				}
 			} );
 		}
@@ -688,16 +698,22 @@ export default class Editor {
 		connectSubmitButtonObserver.call( this );
 
 		function connectSubmitButtonObserver() {
-			const button = this.dom.getSubmitBtn();
+			this._submitButtonObserver = new MutationObserver( () => {
+				// noinspection JSPotentiallyInvalidUsageOfClassThis
+				this._setSubmitStatus();
+			} );
 
-			if ( button ) {
-				this._submitButtonObserver = new MutationObserver( () => {
-					// noinspection JSPotentiallyInvalidUsageOfClassThis
-					this._setSubmitStatus();
-				} );
-				this._submitButtonObserver.observe( button, { attributes: true, attributeFilter: [ 'disabled' ] } );
+			// GH messes up with submit buttons as its will, so instead of observe a specific button, we observe
+			// anything in the form that had the "disabled" attributed changed (usually submit buttons).
+			this._submitButtonObserver.observe( this.dom.root, {
+				attributes: true,
+				attributeFilter: [ 'disabled' ],
+				subtree: true
+			} );
 
+			if ( !this.domManipulator._hasSubmitBtnObRollback ) {
 				this.domManipulator.addRollbackOperation( () => disconnectSubmitButtonObserver.call( this ) );
+				this.domManipulator._hasSubmitBtnObRollback = true;
 			}
 		}
 
diff --git a/tests/unit/editor.js b/tests/unit/editor.js
index 51d3faf..0598b0c 100644
--- a/tests/unit/editor.js
+++ b/tests/unit/editor.js
@@ -620,6 +620,22 @@ describe( 'Editor', () => {
 					} );
 			} );
 
+			it( 'should unlock the form on sync', () => {
+				const editor = new Editor( GitHubPage.appendRoot( { text: 'test' } ) );
+				const textarea = editor.dom.root.querySelector( 'textarea' );
+
+				return editor.create()
+					.then( () => {
+						expect( textarea.validity.customError ).to.be.false;
+						editor.rteEditor.setData( 'Changed data' );
+						expect( textarea.validity.customError ).to.be.true;
+
+						editor.syncEditors();
+
+						expect( textarea.validity.customError ).to.be.false;
+					} );
+			} );
+
 			it( 'should unlock the form during submit', () => {
 				const editor = new Editor( GitHubPage.appendRoot( { text: 'test' } ) );
 				const textarea = editor.dom.root.querySelector( 'textarea' );
@@ -636,11 +652,55 @@ describe( 'Editor', () => {
 					} );
 			} );
 
+			it( 'should lock/unlock the form when switching modes', () => {
+				const editor = new Editor( GitHubPage.appendRoot( { text: 'test' } ) );
+				const textarea = editor.dom.root.querySelector( 'textarea' );
+
+				return editor.create()
+					.then( () => {
+						editor.rteEditor.setData( 'Changed data' );
+						expect( textarea.validity.customError ).to.be.true;
+
+						editor.setMode( Editor.modes.MARKDOWN );
+						expect( textarea.validity.customError ).to.be.false;
+
+						editor.setMode( Editor.modes.RTE );
+						expect( textarea.validity.customError ).to.be.true;
+					} );
+			} );
+
+			it( 'should clean the textarea on form unlock', () => {
+				const editor = new Editor( GitHubPage.appendRoot() );
+				const textarea = editor.dom.root.querySelector( 'textarea' );
+				textarea.required = false;
+
+				return editor.create()
+					.then( () => {
+						editor.rteEditor.setData( 'Changed data' );
+						expect( textarea.validity.customError ).to.be.true;
+						expect( textarea.required ).to.be.true;
+
+						editor.syncEditors();
+
+						expect( textarea.validity.customError ).to.be.false;
+						expect( textarea.required ).to.be.false;
+
+						editor.rteEditor.setData( 'Changed data again' );
+						expect( textarea.validity.customError ).to.be.true;
+						expect( textarea.required ).to.be.true;
+
+						editor.syncEditors();
+
+						expect( textarea.validity.customError ).to.be.false;
+						expect( textarea.required ).to.be.false;
+					} );
+			} );
+
 			it( 'should remove "formnovalidate" from buttons on form lock', () => {
 				const editor = new Editor( GitHubPage.appendRoot( { text: 'test', submitAlternative: true } ) );
 				const button = editor.dom.root.querySelector( '.js-quick-submit-alternative' );
 
-				editor.create()
+				return editor.create()
 					.then( () => {
 						expect( button.hasAttribute( 'formnovalidate' ) ).to.be.true;
 						editor.rteEditor.setData( 'Changed data' );
@@ -652,7 +712,7 @@ describe( 'Editor', () => {
 				const editor = new Editor( GitHubPage.appendRoot( { text: 'test', submitAlternative: true } ) );
 				const button = editor.dom.root.querySelector( '.js-quick-submit-alternative' );
 
-				editor.create()
+				return editor.create()
 					.then( () => {
 						expect( button.hasAttribute( 'formnovalidate' ) ).to.be.true;
 						editor.rteEditor.setData( 'Changed data' );
@@ -820,11 +880,19 @@ describe( 'Editor', () => {
 
 			it( 'should check other required elements (empty)', () => {
 				const editor = new Editor( GitHubPage.appendRoot( { text: 'Test' } ) );
-				editor.dom.root.insertAdjacentHTML( 'afterbegin', '<input value="" required>' );
+				const other = createElementFromHtml( '<input class="test-el" value="" required>' );
+				editor.dom.root.insertAdjacentElement( 'afterbegin', other );
 
 				return editor.create()
 					.then( () => {
 						expect( editor.dom.getSubmitBtn().disabled ).to.be.true;
+
+						other.value = 'Something';
+						editor.rteEditor.ckeditor.fire( 'change:isEmpty' );
+						expect( editor.dom.getSubmitBtn().disabled ).to.be.false;
+
+						editor.rteEditor.setData( '' );
+						expect( editor.dom.getSubmitBtn().disabled ).to.be.true;
 					} );
 			} );
 
@@ -884,35 +952,33 @@ describe( 'Editor', () => {
 			} );
 
 			it( 'should observe external changes to submit.disabled', done => {
+				// The root textarea has "required".
 				const editor = new Editor( GitHubPage.appendRoot() );
 				const otherInput = createElementFromHtml( '<input class="test-el" value="" required>' );
 				editor.dom.root.insertAdjacentElement( 'afterbegin', otherInput );
 
 				editor.create()
 					.then( () => {
-						expect( editor.dom.getSubmitBtn().disabled ).to.be.true;
+						expect( editor.dom.getSubmitBtn().disabled, 'disabled start' ).to.be.true;
 
 						otherInput.value = 'Testing';
-						expect( editor.dom.getSubmitBtn().disabled ).to.be.true;
-
 						editor.dom.getSubmitBtn().disabled = false;
 
 						// Mutation observers are asynchronous, so we should still not see the editor fixup here.
-						expect( editor.dom.getSubmitBtn().disabled ).to.be.false;
+						expect( editor.dom.getSubmitBtn().disabled, 'disabled after mutation' ).to.be.false;
 
 						// So we use a timout to give a chance to the observer to be invoked.
 						setTimeout( () => {
-							expect( editor.dom.getSubmitBtn().disabled ).to.be.true;
+							expect( editor.dom.getSubmitBtn().disabled, 'not disabled after mutation' ).to.be.true;
 
 							otherInput.value = '';
-							expect( editor.dom.getSubmitBtn().disabled ).to.be.true;
-
 							editor.dom.getSubmitBtn().disabled = true;
+
 							setTimeout( () => {
-								expect( editor.dom.getSubmitBtn().disabled ).to.be.true;
+								expect( editor.dom.getSubmitBtn().disabled, 'stay disabled' ).to.be.true;
 								done();
-							}, 0 );
-						}, 0 );
+							} );
+						} );
 					} );
 			} );
 		} );