Yeah, check your primary and critical rails so it may help in narrowing it down. Check resistance relative to ground at the following locations - On the inductors surrounding the main Max PMIC on the rear of the board, check resistance to ground on 3V3PDR (can be found at pin 6 of M9 IC), check SYS (one side of the large inductor next to BQ) then finally across battery pos & neg connector on the board. If any of these rails show a skewed reading compared to a known good then it’s likely something on that rail causing the isuues.
I will say this is more commonly down to two things, either liquid/corrosion damage on the board (under or around IC’s) or down to poor rework (most commonly M9, BQ, P13) as a result of stray solder or even bridged pins/pads.
Might also be worth checking none of the connectors are scorched or charred.