If i've acccrued pto and my ex-employer is now stating that the accrued pto is incorrect...?

Can they then just not pay me out? I was laid off and was told that I may have been accruing time incorrectly so they may not owe me money but in fact I may owe them money. Does this sound right? I'm in CA. Was also told if they do owe me they can't pay me and will have to work something out. I've contacted people that still work there and their pto time isn't being touched and they are actually hiring. Any help will be appreciated.