Hate to break this to you, but it is probably not as simple as being off track. The lift unit has a plastic wheel around which the cable winds for lifting/lowering the window. It often fails, and it probably can not be repaired, only replaced. The replacement is fairly simple if you have the right tools, you will have to drill out the rivets that secure the mechanism (I believe there are four of them) remove and replace the lift unit, then rivet back in place. The rivets should be 1/4" and that is pretty hefty for most hand riveters, you will need a long-handled hand riveter or a pneumatic tool to do the job.

Best of luck,
g

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64 230sl, my daily driver
94 E500, sold
98 E320, family and dog hauler
04 C240, safe machine for teen drivers, but a poc
08 audi a4, yes we have gone to the dark side