Voles are hard to stop, once they are chomping on your root vegetables.
The first year I planted potatoes, back when Yukon Gold were hard to get, I was digging up my crop and I had the same thing happen. I’d see a GORGEOUS, HUGE potato - and the underside would be GONE! So frustrating!
The best ways to prevent this in the future are listed in the link below. When I plant potatoes in raised beds, there seems to be less of a vole problem.
https://bonnieplants.com/gardening/keeping-voles-out-of-the-garden/
The cats and the two house dogs have been patrolling for Chipmunks; they just LOVE to dig up my freshly planted things. Jerks!
NW....forgot my own suggestion for noting region of country first when posting.