Is there a reason why my Multibit Classic does not decrypt my wallet, otherwise a wrong password?

I entered my password in the Delete Password field. The response I receive is "Password deletion failed." The error was "Unable to decrypt bytes". I am 99.9% sure that the password is correct. Are there any other reasons that an incorrect password could be the cause? For example, does the fee need to match current Bitcoin fees? Should the wall be online and synchronized?