I concur. The focusing has likely jumped a tooth on one side. The Wista DX is not very hard to work on in this respect, so give it a try yourself before sending it in for an expensive repair. There's really not much complicated in the focusing mechanism: a rack-and-pinion gear system and a wooden bed that slides inside another. Finding the problem shouldn't be too hard if you're even a little bit mechanically inclined.

Best,

Doremus