Erm I'm a bit confused about this...
Performance mode works bang on for me, I don't use midi so I've not seen this but if true I agree needs sorting.
Performance mode is perfect for me too. But yes, I can confirm that if you throw loads of MIDI at the Kemper it will crash and needs to be turned on and off.
I run a decent midi footswitch and a different 'page' for each song. That page sends performance changes to the Kemper, midi to the DMX lighting controller, digital mixer, Boss SY200 synth pedal and even a sample player. If you scroll rapidly between songs, Kemper death occurs. This isn't an issue live as our set list is in order but at home it can occur.