Do you have light soil. You probably have an extreme nematode problem and while they will affect a lot of crops they really, really affect root crops.
My problem with root crops has nothing to do with the soil, it all has to do with the farmer (me).......
I have this “visual” need with my crops and so the root crops just don’t work for me. I get potatoes up the yingyang from the farmers I know, so buyin onions, garlic, and carrots is realy not that big a deal to me. I’m doing pretty danged good if that is all I’m buying.