the window from popping off the rail when you put the window up. Any advice?

The issue I seem to be running into is my window can go down but it doesn't go down straight nor does it go back up straight. I'm tired of having to leave that window up no matter how hot it is out. It's off track but no matter how many times you put it back on track, it'll pop off. I put a new regulator in with new pivot clips. I had my mechanic look at it and on the left side he said something is suppose to be there that's suppose to prevent the window from popping off the rail when you put the window up. Any advice?

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[Nick at Pelican Parts]

Sometimes the guides that hold the front and back of the glass have moved outward and allow the glass to fall off the track

- Nick