Do both of these engines have barely any run time on them?…..are they fairly fresh out of the box?……if you’re convinced the boards are toast, by all means have fun, ….but if these things have practically no run time, but back & forth on a test track, I’d run the snot out of them for a while on a layout before I go cussing a board out,….😉….if they ain’t been PM’ed ever, lube them up and let them eat for a while, and recheck to see if they smoothed out,….I’m not the electrical wizard, but I’ve only seen two kinds of PS2 5V boards,….good ones, or dead ones….just a suggestion,….
Pat