I was thinking about the ubtest results and it seemed odd that the stable build would have the failure that was showing up on every build I tried. So I decided to check every build I had with both cameras, taking notes, to see what might be going on. In my setup both cameras are running off the same power supply. I've not had any issues with both being on at the same time, but tried it with one on and both on. I have a nice table that shows which firmware version and the results with one camera on and both on. If I had any doubts I was going to switch to battery power and repeat. As it happens, there is no need for the table.
All tests passed with all firmware versions. No failures. That is until I switched back to 100g-1.3.0-4075. Sometimes it would pass, sometimes it would crash, sometimes there would be the exposure count failure. At first it seemed that when you started in play mode it would crash, then the first time after that starting in record mode it would have the failure, then it would pass. However, I could not get the camera to crash when starting in play mode with any reliability.
So then I tried 100g-1.3.0-4043. First test crashed the camera, second test had one failure, third test passed.
I've run the test several times on the other G9 with 100h-1.3.0-4075 and haven't had any failures or issues. I'm wondering if it could be this particular camera with the 100g firmware in it. I'm tempted to update the firmware on the g version to the h version but don't want to take a chance bricking the camera if it does have a problem.
I still have the issue where after a shot or two with CHDK PTP the live view stops updating and you need to go to play and back to record to get the camera paying attention again. If you don't take any shots after putting the camera into record mode the live window keeps updating but the camera will not respond to commands after a while. You have to go into play mode and back to get it to work again. This happens with both trunks. 1.3.0 using local cmd = ("shoot -dl -rm") or "shoot" to take the shot and 1.4.0 using the JPG Remote Shoot function to take the shot.