I have an LX600, but it also has Starlock which works in a similar fashion the LX850. I've found that getting the Starlock focused correctly and training the drives are the two most critical items for getting the tracking working correctly. If either of these are not right, all sorts of weird tracking symptoms occur.
I recently had some tracking problems. At Meade's recommendation, I did a Reset (which cleared all old training and calibration data), then did the Dec Training twice in succession (my scope had been wandering in the declination axis). This seemed to clear up the issues. Also, I had been having trouble with the ARC completing and after this fix the ARC now completes. BTW, the ARC takes longer than the manual says it does. It takes 2 - 3 minutes for each rate to complete, not one minute as the manual states. My PEC training also had trouble completing before the fix and now it completes correctly (and also takes longer than the manual states). One other thing - the training seemed to work better after I had set the Anti-Backlash. Maybe a coincidence since I thought the Anti-Backlash only applied to the handset buttons?
Last year I had problems with the automated Polar Drift Alignment. I found that my Starlock narrow angle scope was two turns out of focus. I used the Starlock utility during the day to focus on a mountain top 10 miles away. After that, my Polar Drift Alignment started working correctly.
If you concentrate on training the drives and getting the Starlock focused, your problems may get solved. Anyway, it's a lot easier than sending the Starlock in for repair!