Divergence between `storedBalance` & actual balance of the join

[iamsahu]

It was observed that there is a substantial difference between the storedBalance & actual balance for the USDC Join as seen in the screenshot below.

Here are the observed balances:
Actual: 1090083323385
Stored: 1090078308254

[alcueca]

We need to find transactions that leave this kind of dust in the joins. We can either trawl the blockchain, which sounds complex, or set up alerts on Tenderly (maybe with help from OnChainTest.sol)