Thanks WilliamM. The adjuster seems to be Okay - no slack in its positioning - and I have it up in the highest position (the same problem happens in the lowest position.) The back of the rack is sagging just as you said. If I press down VERY firmly on the front of the rack when it is slid all the way in, the back lifts up enough and the probe tube becomes aligned with the hole in the manifold. And the spray arm no longer hits the retainer. I can't figure out what can be causing this slack and the entire rack to be tilted.

I have a Kenmore Ultra wash with an upper rack spray arm that hits the manifold retainer (8268325) and this causes stuff to remain in some of the glassware. All of the parts are intact and there appears to be plenty of pressure from the pump. The manifold retainer and the spray arm mount are fine. As the upper rack is seated, the probe tube (8268328), gets lifted up about 1/2 inch out of the manifold retainer in order to align into the holes of the water feed tube (98575974) in the rear. This raises the manifold just enough for the spray arm to hit the retainer. Since the holes (1 for each position on the upper rack) in the rear feed tube cannot be adjusted, it looks like the upper dish rack or at least the height of the spray arm, has to be raised so the arm stays level when the rack is pushed in.

The rack rollers are fine, although there is a fair amount of play in the rollers.

Wondering if a new manifold retainer or manifold would fix this? I don't even know if I can get the parts anymore so any suggestions would be great.