I still get this glitch in the 1.2.0 MV demo.
To replicate the bug easier, I edited the minotaur attack in the database to max so that it would do mortal damage to a party member straight away.
I then just sat on that soon to be dead party member's command selection window until they reached 0 HP, then if I tried to proceed and select 'guard' for example, it would throw up an error. I assume because a now dead actor is trying to do something (guard in this case)