Erratic W126 sunroof

I see lots of different sunroof woes here. Here's another. Sunroof most often opens slow and/or choppy. Isn't popping up without a helping hand, either. But always closes smooth and steady. Weird. Have also noticed if car is moving forward, roof almost always opens perfectly. If braking, sunroof barely moves and doesn't always open fully. Have lubed with white lithium grease and/or silicone sprays (and I always clean tracks before lubricating). Any advice?


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Rob
1991 300SEL