My bsd suffered from resets at 4.9. I replaced the bridges and caps and no more resets. As it was explained to me, the voltage is dropping quicker than a dmm can register. So while it shows 4.9 it may drop much lower for a bit. But it happens so fast the dmm can’t see it and display in time.
Honestly I would replace the board. And either fix the old one or get another as a spare.