Submitted by xiaoming90, also found by berndartmueller
https://github.com/code-423n4/2022-06-notional-coop/blob/6f8c325f604e2576e2fe257b6b57892ca181509a/index-coop-notional-trade-module/contracts/protocol/modules/v1/NotionalTradeModule.sol#L309
https://github.com/code-423n4/2022-06-notional-coop/blob/6f8c325f604e2576e2fe257b6b57892ca181509a/index-coop-notional-trade-module/contracts/protocol/modules/v1/NotionalTradeModule.sol#L385
Whenever a setToken is issued or redeemed, the moduleIssueHook and moduleRedeemHook will be triggered. These two hooks will in turn call the _redeemMaturedPositions function to ensure that no matured fCash positions remain in the Set by redeeming any matured fCash position.
https://github.com/code-423n4/2022-06-notional-coop/blob/6f8c325f604e2576e2fe257b6b57892ca181509a/index-coop-notional-trade-module/contracts/protocol/modules/v1/NotionalTradeModule.sol#L309
The _redeemMaturedPositions will loop through all its fCash positions and attempts to redeem any fCash position that has already matured. However, if one of the fCash redemptions fails, it will cause the entire function to revert. If this happens, no one could purchase or redeem the setToken because moduleIssueHook and modileRedeemHook hooks will revert every single time. Thus, the setToken issuance and redemption will stop working entirely and  this setToken can be considered bricked.
https://github.com/code-423n4/2022-06-notional-coop/blob/6f8c325f604e2576e2fe257b6b57892ca181509a/index-coop-notional-trade-module/contracts/protocol/modules/v1/NotionalTradeModule.sol#L385
User will not be able to purchase or redeem the setToken. Users fund will be stuck in the SetToken Contract. Unable to remove matured fCash positions from SetToken and update positions of its asset token.
This is a problem commonly encountered whenever a method of a smart contract calls another contract  you cannot rely on the other contract to work 100% of the time, and it is dangerous to assume that the external call will always be successful.
It is recommended to:
ckoopmann (Index Coop) acknowledged, but disagreed with severity and commented:
ckoopmann (Index Coop) confirmed and commented:
