Quoted from 80spit:just looking for some guidance where to go next
Post some clear high resolution pictures front and back (preferably taken outdoors in shaded daylight) of the MPU board.
Are the flickering controlled lamps LEDs or incandescents?
You'll need a logic probe to diagnose this.
Your problem sounds familiar:
https://pinside.com/pinball/forum/topic/big-game-mpu-200-issues#post-5616331