Can't help with the diagnosis, but gotta say that's a cool optioned truck with the 5.9L Magnum. Can't be too many of those left. Good score and good luck.
Sounds like the original door was manual operation and sometimes later a prior owner added the electric assist to what sounds like a finished garage. To accomplish the installation, a half *** 2x4 was added as a support. So after typing that, I'm sure everyone is going "no $heet Sherlock".
I...
I also buy at O'Reilly's and open the box there to check. Not only for Made in USA, but to make sure that I am getting a new, unused, correct filter
I've noticed that the O'Reilly's shelf stockers get a little overzealous with the box cutters too.
No photos but I did mine to sorta match my brothers 73 340 Cuda. Of course there were no 340, road wheels, factory stripes or Internet back in the 80s. Only thing was mail order thru Scale Auto Enthusiast.
Really wish that MPC Round 2 would reissue that kit. Be even better with a raisen bran hood. Even though the motor and chassis are generic, that kit has that certain allure the others (monogram, Johan, revell, and Lindberg) don't.
Return may be free but not hassle free lol. Go to staples, wait in line in what seems like forever. UPS store I think wants their cut, which means fee. PITA.