Couple of thoughts, I'm not sure if these are related to your problem but I thought that I would share them just in case.
1) One time when I was using a MIDI controller (before I got the Kemper Remote) and I accidentally misaligned the MIDI cable when plugging it into the controller and IIRC it acted like you described. What happened was the MIDI controller had a 7 pin socket because it supported phantom power, I was using a 5 pin cable and somehow had it misaligned when I plugged it in. MIDI connectors do have a key so you shouldn't be able to do that but somehow I did
2) I discovered by accident that if you turn the master volume knob on the KPA while it is booting it won't boot correctly. This makes me wonder if your controller was sending commands to the KPA while it was booting causing it to lock up, I'm not sure if MIDI commands would affect the KPA like turning a knob on the front of the KPA but it might be worth investigating. BTW, I did report this and Kemper support was able to duplicate the issue so I'm sure that they will address it in a future update.