During execution of operations on sub-accounts, the fallback handler and guard are not allowed to change:
TransactionValidator::_checkSubAccountSecurityConfig:
Here, the guard and fallback handler are verified unchanged to what is defined in the address provider service.
The issue is that if governance changes the implementations of either of these, this check will fail for all existing sub-accounts; since they are created with what was the guard and fallback handler at time of safe creation.
The sub-accounts are blocked until the console account updates the guard or fallback handler on the sub-account.
Changing the address of either SafeModerator or ConsoleFallbackHandler will break every existing subAccount. It also forces the owning console accounts to upgrade to the new implementations without any opt-in.
Consider storing the values in pre-validation and do the comparison against the stored values in post-validation. That way, they are independent of any changes from the protocol.
