Submitted by oakcobalt, also found by SpicyMeatball
Code references: 
YieldStakingBase::collectFeeToTreasury will attempt to transfer funds that are not available, resulting in repetitive revert.
The vulnerability is totalUnstakFine is incremented in the unstake flow by the botAmin. Note that the fund is not available at this point until later when the withdrawal can be claimed in repay flow.
YieldStakingBase.sol#L357
In collectFeeToTreasuy, the transfer amount is totalUnstakeFine - claimedUnstakeFine which includes the funds that are not ready to claim.
YieldStakingBase.sol#L171
Vulnerable cases:
collectFeeToTreasury might face repetitive revert or even DOS. protocol funds can be locked.
Consider only incrementing totalUnstakFine in _repay. The increment amount is the actual funds that are claimed or covered by the user.
thorseldon (BendDAO) acknowledged
