not that, its a small round beetle, a rather good looking one, not some nasty bug. Something like a ladybug thats somewhat larger
I can't find where it got burned. And I did coat everything in silicone MG chemicals PCB protectant BTW, everything I can
I did probe the signal, it basically square wave coming off the boost board.
Right now what I am going to do is use conformal coating remover to get rid of all the manufacturers varnish on the boost card, I will give it another try (in case the varnish went bad, sometimes bad varnish can conduct). If it still does not work, I can actually probe it safely without varnish, because probing it through the varnish while its running with 810VDC rails .... is a rather stupid way to have an accident because you need excess pressure
Applying that varnish is not easy, not the ones that are slightly softer. I actually have some peeling on the back of the main board I did last year. I guess it was not clean enough. My work on the control card, and the IGBT snubber board (IGBT controller), looks nice and intact. I like the MG chemicals silicone that comes in a small bottle with a nail polish brush on it.
Now, if I really wanted to protect it, I think I would use red insulating varnish aka transformer varnish... but it makes things look like some bronx boiler room. Its like the "i don't give a fuck" paint they put on cinder blocks in apartment hallways .. nothing shows class like painted brick. I am scared a crack dealer might try to setup operations

What happens to millers default varnish they supply the unit with
1) PCB is too hot, there is too much corrosive dust
2) varnish turns yellow
3) varnish peels
4) I am suspicious it becomes conductive slightly to 810VDC. I saw evidence of electricity in the varnish near some HV parts, like soot and black cracks

5) boards look like a burn victim
Basically the history is
1) get machine with 4 damaged cards, had to repair the MCU card diode, the main board flyback, and something on the igbt controller.
2) fix what I can, replace basically all the parts on those 4 boards, fill in holes with 270dp epoxy and fiberglass after cleaning with micro mill.
3) have to replace the inverter control card for $$$$, even though I replaced every part on the old one (every part), and cleaned / milled the soot off, including grooves between some burned traces, it would not work.
4) got it working with new card + my repairs
5) take apart everything and wash it, paint a few rust spots on transformers after cleaning, etc, and siliconed the 3 cards I worked on, *left the new inverter card, the old booster card alone.
6) polish all the connectors, grease everything up, reassemble
7) works

breaks and this thread begins
SO I left the Boost card alone, because it looked nice, the unit worked, and the conformal coating looked nice. Now the symptoms are linked to boost card, meaning it was probobly damaged to begin with but still functional enough to weld.