[GriffinRU]

Wow, Gentlemen’s, new BK-Electronics controllers come equipped with bigger heatsinks and fancy epoxy...

Short story, as Daniel said, with bad NiMh you can make this combo fail miserably at full throttle. Good batteries or LiPo - no problem.
In addition UBEC wasn't soldered, just twisted wires and heatshrink - not good.
Heatsink was completely loose inside heatshrink.

I do not see any reasons to take controller completely apart, but going to restore programming jumper, replace top capacitors with newer ones (560uF 35V), add TVS and fix power and UBEC wiring. And put heatsink back.

I will upload results later,