Trying to sell our totaled car. Spent 2 weeks goin...

Trying to sell our totaled car. Spent 2 weeks going back and forth with them to make sure all the paperwork was in order because owner is out of country and we wanted to make sure we had everything so we just mail the paperwork once for them to sign. Then paperwork comes back and it turns out there's another crucial form they didn't tell me about for 2 whole weeks. Not once was it mentioned. Now I have to waste 3 more weeks and another $60 (now total $120) to send this paperwork for the owner to sign. All that for $300 for a totaled car.