Been there, but got lazy and lived with it.

Do this - while pulling up on the driver's door knob such that all the doors should be opening, pull up on the left rear door knob. Determine if the LR actuator is trying but can't do the job.

That old lube or grease of whatever gets in there can become pretty solid in 21 years.

So if it is not an electrical probem, you will need to remove the door trim panel and lube things in there. Maybe drip some real thin oil, like 3-in-1, so it can get into where the old grease is and thin it out a bit.

My RF door was the same on my 1988 244 when I got it i 1998. Over time it has begun to work on a pretty consistent basis.

Good Luck,

Bob

:>)