Just got a 1997 vintage LD-V4300D, and upon first firing it up ran into a skipping problem. It would play the first few minutes of the disk okay, but then would get stuck in an endless loop of skipping backwards about 300 frames (on a PAL CAV disc). Skimming a few other posts suggested the laser sled rail might need lubricating.
So popped off the hood, taking great care to avoid eye-contact with the laser. Player was very clean inside (almost no dust), so it was unlikely cleaning was required. Quickly powered on and off, so as to leave the travel lock (looks like a bear trap!) in the open position, then carefully slid the laser sled backwards and forwards a few times. Spun up a disc and problem sorted.
The player had probably been sitting idle for quite a while so possible the head had got a bit stuck in place, certainly it didn't feel stuck when I moved it.
Anyway - I hope that helps someone.