Brother P touch 85 label maker with BAD keys 

Thanks! Had simular problem on p-touch 65. Root cause was a leaking battery which damaged the printed wire board. Although not visable under a microscope, after measuring the connection seemed to be broken. Like you, I soldered an extra wire in parallel to the printed wiring board, which solved the problem.

My P-Touch PT1000 now has the exact same issue. In fact, all of the lower keys stopped working. I'll trouble shoot like how you did it. Great video!

Great troubleshooting video. I'm going to check PCB one more time...