Not really sure if this is a bug or, what I like to call in my software, an “undesired feature”.
If APPR is accidentally pressed while at cruise with A/P set, it will give the warning about speed too high to activate APPR. It will also deactivate A/P as it tried to set up APPR and then disengaged it.
Shouldn’t it check the flight parameter and warm you that it can’t be set without starting the activation followed by deactivation and losing A/P completely? Or just grey out the APPR button until it can be activated so it isn’t accidentally pressed?