I had these symptoms and asked my dealer (Keystone). they suggested I try wiggling the key up and down in the lock. It worked. Eventually I ended up replacing the electrical connections on the lock and this fixed the problem. Apparently this is a known issue.

good luck.

ABS module
Tailgate innerpanel repair kit
pcv system

You will need to remove the two torx on the outside and it does come out from the inside. You need to carefully pull back the right inside panel to get to the area near the fuel door. To do this requires 1) popping up the bottom panel next to the spare tire 2) taking off the back corner panel with t...

My 850 had a jammed fuel door lock and had a parasitic battery drain. It would continue to draw 1.3 Amps after the doors were locked. The battery drain changed to 0.02 amps once I repaired the fuel door lock motor by taking it all apart and lubricating it.

Hope this helps.