I wen through somewhat of the same situation, OA visa then extensions for six years, got to the border and they were making an issue out of my expired re-entry permit, one of the Cambodian Immigration people took care of everything for me, for a few of course, they did the visa, in and out same day and I think I had to pay them 2000 baht, think I could have just walked across the border and saved some money, but my only interest was getting the OA canceled and gladly payed the fee this was in September of 2022