After letting the K5 sit for a few days with the battery disconnected and the display not plugged in, I decided to try it out again with no battery.
Surprisingly I was able to adjust parameters, change MIDI channel turn on/off system exclusive as if all was normal.
Then, suddenly it stopped and I was back to the limited selection, most parameters not working but still able to make a few choices.
So I now believe I do have a functioning unit, yet something is still wrong.
I'm going to try to repeat the last setup and see if I get the same results.