I don't know if this will be useful to anyone, but as a point of reference I've been working all week doing this with no issues. I'm running Cubase 10.5 in Windows 10 with the Kemper in performance mode and the remote connected.
I have a two bar count off, so in that period I fire one CC to select the performance, then two beats later send CC 50 - 54 to select the slot. On some songs I also turn a stomp on / off. Cubase is set for chase to play, so no matter which song I pick (it's all one long sequence) or where in the song I am, the Kemper syncs up to the correct profile / slot / stomp for that song at that point in time.
Per Burkhard's observations, my scenario is very low throughput of MIDI messages, and that might be one reason why it's stable for me.
Another thing to note is that Rig Manager is not running when I'm working in this mode. I've experienced weirdness with RM and the remote connected at the same time, something that seems to be a known issue of sorts. So, if you're having difficulties with MIDI, I wonder if Rig Manager is also connected at the same time. That might be another path to test as you debug the problems.