Sorry but I do have the latest OS version installed in my Powered Kemper (8.7.15.42312) and I had the same thing happen recently.
It has happened twice and interestingly with the same rig.
I have a rig with three profiles assigned to channels 1 2 and 3 of the kemper remote.
The first time this problem happened was when I was on profile 1 and when I stepped on profile 2, the input was terminated. No lights indicating it was receiving a signal from the input.
Changing rigs did not help. Had to shut down the unit and power up again which appeared to fix the problem.
Second time it happened exactly as the first time with the same rig and profile.
Fortunately, the first time was at home and second was at rehearsal
Needless to say, I am extremely concerned this will happen at a show.