Faders and buttons of the master section refused to work.

Today I had to rent a Road Hog 4 to compensate the failure of ours. The rental company does not use nor rent theirs very often, because they barley have customers for it. So the desk was still on V3.8. I upgraded the desk to V3.13 instantly, loaded my backup show (saved from 3.13) and set our lock screen image. After that I noticed that the faders and the buttons of all the playbacks refused to work. :-O All other buttons and encoders were fine. I logged off the show and went back into it. Faders were working then, but the buttons still showed no reaction. I logged off again and went into surface test mode...everything fine there. So I shut down the console completely, left it for a minute without power and started again. Since then all worked fine.
What could have happened there?