Caps is just a wild guess, I wish I know how to narrow that down.
I spent more time testing firmware and noticed that VERY first rev10 firmware also boots fine EVERY TIME (Bus Pirate 5 auto build: main branch - #61 by ian), and I think this is because it doesn’t try to blink all leds before boot like recent firmware does. Maybe it is over-current in some component that is causing everything to halt?
P.S. I put LED back after fixing pads, and entire chain works now (only with REV10 or soft reset obviously)