I immediately try it and found that it does reduce stray coupling from the board.
Unfortunately, the noise is still persists.
I later found that it is actually the high impedance balance leads that cause significant voltage drop every time the bridge transitions.
*Partition analogue and digital grounds
*Provide some power decoupling for the opamp
*Stiffen the supply rails for the synchronous buck converter chip
*Add flyback diodes to catch fast bemf
*Maybe replace the balance leads with lower gauge