Here's what I did... Had the exact same thing, and eventually it would stop going up or down if it got into too big a bind.
Used a coat hanger and wrapped it around the motor and gear to hold the two in place. Used it like one of those wire tie wraps on a garbage bag. Trim it off making sure it doesn't hit anything with the window moving up and down, and you're all set. It's been probably 3+ years now - it's given me no problems since.
Scott
'93 525iT
132k