Submitted by shw, also found by cmichel
The supplyTokenTo function of SwappableYieldSource assumes that amount of _depositToken is transferred to itself after calling the safeTransferFrom function (and thus it supplies amount of token to the yield source). However, this may not be true if the _depositToken is a transfer-on-fee token or a deflationary/rebasing token, causing the received amount to be less than the accounted amount. SwappableYieldSource.sol L211-L212
Recommend getting the actual received amount by calculating the difference of token balance before and after the transfer. For example, re-writing line 211-212 to:
PierrickGT (PoolTogether) confirmed:
