Submitted by peritoflores, also found by JC and StyxRave
https://github.com/code-423n4/2022-05-backd/blob/2a5664d35cde5b036074edef3c1369b984d10010/protocol/contracts/swappers/SwapperRouter.sol#L140
https://github.com/code-423n4/2022-05-backd/blob/2a5664d35cde5b036074edef3c1369b984d10010/protocol/contracts/swappers/SwapperRouter.sol#L280
Usage of deprecated transfer Swap can revert.
The original transfer used to send eth uses a fixed stipend 2300 gas.   This was used to prevent reentrancy.   However this limit your protocol to interact with others contracts that need more than that to process the transaction.
A good article about that:
https://consensys.net/diligence/blog/2019/09/stop-using-soliditys-transfer-now/.
Used call instead.  For example
chase-manning (Backd) confirmed 
Alex the Entreprenerd (judge) commented:
