I'd call it BTANB* until further proof.
*: Bugs That Are Not (emulation) Bugs: Bug on real handheld that doesn't happen on MAME.

Segments are grouped together, in this case it electronically doesn't make sense to swap left power bar with right.
Issue with decap/optical dump? Looking at the decap, it was good quality, I always double check them.
Consider a SM510 emulation bug? Unlikely, the opcodes are pretty simple and all other games work fine on MAME.