Users can lose their CREDIT tokens by calling or donateToTermSurplusBuffer for a non-existing term and transferring their tokens to the wrong or eventually non-existing address.
ProfitManager.sol#L258-L264
They wont be able to rescue their tokens unless contract/user with GUILD_SURPLUS_BUFFER_WITHDRAW role calls it for a user who has lost his tokens.
ProfitManager.sol#L277-L287
Consider adding check if term is actually a LendingTerm contract, modify donateToTermSurplusBuffer:
