2003 GMC Sierra 1500 "right rear door ajar"

[Sunshine70]

I have a GMC Sierra 1500 Quad cab & in the last couple months whenever i start my truck & put it in reverse it starts ding, ding, ding & the error "right rear door ajar" comes on. This affects my interior lights & i have to turn the override light switch to turn the interiors & dome light off. This is a major pain in the ass especially when i work night shifts & have no interiors till the vehicles on & in reverse. I have changed the door latches twice now. The first time it seemed to work but within a few weeks the error came back again. Just recently I changed it again but it was a big fail! Please, please, please if anyone has any tips, tricks, comments please let me know...this is driving me nuts!