Debugging HID/Keyboard with serial to another Puck?

So any thoughts… problem with the firmware, or problem with my code? Or, my code is doing something legal but unexpected, perhaps? Hngh.

Re: multimeter, good tip! I was thinking that, but was intending instead to hook it up to another Puck (or possibly a Pico or Original) to do voltage monitoring and graph it over time to get some idea of likely battery life. However, with the preliminary check with the multimeter being two or three levels of magnitude more than I was expecting, I figured I'd raise that before I went too far with it.