Been there, done that, hat and t-shirt...

Our 98 did the same way back. Behaved just as you describe. Once it let go and was clear what the problem was, I found hinges for ~$125 a shot. Wasn't in my budget to plunk down that cash. Kept the door closed for a couple of months until I finally found a yard on Car-Part.com with a wrecked door who was willing to sell just the hinges. This was before the days when I started to hit up U-Pull-its.

One idea might be to check Car-Part for someone with only the PS side of the rear section showing as good, and then no tailgate, suggesting is was rear-ended on the DS. See if they have a wrecked gate with hinges still good.

The older hinges have a pin hole to lube through. Never seen an older one fail. Been a couple of newer ones without fail though. Bet they saves $0.05 not drilling...