window arms popping out of tracks

Hi, the long arm with the angle near the crank has a small plastic wheel which rides in a channel under the window; these pop out of the track where there is a small cutout in the side of the track where the wheel would slide thru to install into the track. The arms have a bit of vertical 'looseness' in them, probably from age (15 yrs or so). I've tried gently bending the arm that rides in the track up a little, to no avail. I didn't see a part number, but here are some pictures (2 different size windows). I didn't see the exact configuration arm assy on your website. Could you please advise if there is a way to tweak them to work, and if there are exact replacements available?
Thanks