Well, the first thing I would check is the three small lytics across the motor coils. Looking at them on a print you almost can't tell what they're for but I think they keep switching noise out of the Hall effect sensors. When they open up they do very strange things to the servo circuit. Very unpredictable things.

Exactly why this doesn't affect cue and review, forget about trying to figure that out, it is either the problem or it isn't.

There are four reference frequencies for the heads, different speeds for cue, review, pause and normal play. That may be why is only play is affected.

And I will tell you this, when a VHS has more than a certain number of hours on it, do not use review. The tape path wear causes problems and usually does cause the tape to ride up in review. Unless you want to replace practically everything, just forget it. I'm not sure exactly what wears out but I think it is the lower drum and the bottom of the ACE head, something like that. For some reason even on full loaders (ones that stay loaded in FF and REW) as long as the pinch roller isn't engaged it is fine, but you just can't get the friggin tape tension right top to bottom. Like I said I suspect it is due to lower drum wear and you don't want to try to find one of those. You can feel with your finger on most of these that the tension at the bottom of the tape is higher than the tension at the top. This normallly wouldn't make sense but I believe the problem is that the fine finish is worn off. That causes more drag. The ONLY other thing is could be is a lack of backtension on the takeup reel in review. Either way, it's just not worth dealing with.

These things are so old and unreliable at this point their main function is to dub to DVD.

One possible test to see if it may be those caps on the drum motor is to use your finger to put a little drag on the drum as it plays. If the speed stabilises, there is a good chance it's those caps. They're usually low value, like maybe 0.47 to about 3.3 uF so testing them with an ESR meter is largely inconclusive.

Give it a shot, and if someone wants to use review tell them to dub to DVD and do it on that. Seriously, don't waste your time trying to get new performance out of a worn out tape path. That aluminum is so damn soft that when you get the really grungy heads and have to scrub with the coffee filter or whatever, the black stuff is actually the aluminum. The oxide from the tape is brown.

Of course if you have to scrub the upper drum like that the coffee filter is stationary and you turn the drum by hand. ALWAYS COUNTERCLOCKWISE. Many have "swept back" heads and if you turn one of those the wrong way it'll catch and wreck it.