Pops out of reverse and 5th is sometimes hard to get into.

Trans internal failure.

Sounds like the shift fork is failing or the slider for that fork. Should be same fork and slider for 5th and reverse

Sounds like the sink rows are going out or has a warn shifter fork if you can get all gears without running it needs a cluch

Internal wear

Time for a rebuild most likely

hi check the gear linkage at the gearbox im sure the small rod has popped off same rod for 5th and reverse maby need replaced will only happen again

Not sure about popping out of reverse. But 5th gear pop out is a problem on these, nissan never had a recall, but they offer a slightly altered version of the 5th gear that is available. Go read up at nissanforums there's a lot there, pics and all, even a petition to Nissan for everyone who's had the same problem, me included.

your tranny synchronizing bearings are going out most likely. usually it starts getting hard going into reverse then sometimes into fifth and grinds as it gets worse. something to help with it will be when you first start the car just put the car in 5th gear before you go into reverse that allowsyour bearing to align and ussually allows it to go in more freely.

no. linkage most likely you need to get adjusted or
one of it is worn out

Only 2 thing cause this, worn engagement dogs on the gear pack or worn shifter parts or both, how many miles?

The transmission type wasn't specified as to manual or automatic,as both were available on 91-96 Stealth's,but from the complaint,i presume manual trans.If it is the manual trans,5th gear and Reverse gear are usually on the same shift rail.So part of the diagnosis is to pay attention to 5th gear for any problems.Another part of the diagnosis is the clutch pedal and hydraulics that activate the clutch.When the problem is happening,try this:pump the clutch pedal rapidly,and repeatedly,then try to engage Reverse.If it goes right into Reverse,then the clutch hydraulic system needs to be inspected.Good luck.