Pulling my hair out

If you think you have a launch related electrical issue you could do a bit of an oddball thing...

One at a time on each electrical component, battery too, rotate them 90 degrees to their current orientation (horizontally)

If a battery cell is shorting and the battery is mounted such that the forces at launch cause a plate to move for and aft, rotating it 90 deg should eliminate that movement.

It's a PITA but might pinpoint an issue.

You could do all components that way at once and un rotate one at a time if the problem goes away.