How hard is it for you to move your shifter from neutral into reverse?
From day one, putting my car into reverse has been a challenge. No grinding of gears, clutch pedal travel is fine, clutch appeares to be okay. It just takes a tremedous amount of force to move the shifter into position.
How hard should it be?
(all other gear selections are fine)
Maybe your reverse light switch is stuck/tight? Try taking it out and shifting once. It's on the upper driver's side of the tranny, kinda tight up there though. I have no idea if this will actually work, just a thought.