Thank you for that video I have watched that video among other videos a zillion times I just do not understand what I'm doing wrong. Just when I think I got it it just slips out of reverse. Or it will act like it's in reverse the reverse lights will go on in the back but it won't engage the gear it won't move
take the cable off down at the transmission, then move it by hand and compare it's location to the cable connector. you either have it adjusted to far forward or to far back. I suspect too far back. you might want to get a helper to move the shifter while you are under the truck and feel it/look at it.
of course don't get rolled over, chock the wheels.....]
when you move the shifter arm at the transmission you will feel it "click" at each gear, I suspect how the cable is set currently it's not "clicked" into reverse so it pops out into neutral ? correct? if not then it is popping back into park in which case the cable would need to be adjusted the other direction.
it's going to be one way or the other..