Take a look at https://github.com/code-423n4/2024-03-zksync/blob/4f0ba34f34a864c354c7e8c47643ed8f4a250e13/code/system-contracts/bootloader/bootloader.yul#L1937-L1962
This function returns whether the mimicCall should use the isSystem flag, issue here is that this statement // Note, that this point it is not fully known whether it is indeed the selector... and should instead be // Note that, at this point it is not fully known whether it is indeed the selector...
Bad code structure, harder to understand code since integrators would assume one is talking about the unread memory point at the end of dataLen
Apply the fix.
