It sure sounds like a problem. I had a 2000 Gerogie Boy w/V-10, it acted that way after the transmission blew the transfer from 3rd to OD and OD back to 3rd. Ford wanted about $3,500.00 for a rebuilt transmission. But, I was lucky to find a shop in Tucson that rebuilt it for about $1,600.00.
I would have a transmission shop put it on their tester. It could be a speed senor, there are two on that type of transmission.
2008 36'QSH Phaeton