Pwr window broke. Parts question...

[1980SC]

My passenger side power window broke today. It seems the problem is the bottom rail which holds the glass, will not stay attached to the regulator 'X' piece.

When I try to raise/lower the window, this rail falls to the bottom of the door.





Here is where the rail should stay :





Is this rail part of the window regulator, or does it have a name of it's own? Is there supposed to be something that keeps it from sliding off the 'X' piece? Nothing appears to be broken, and the window functions okay in the driveway. Once I go for a drive though, that rail crashes down inside the door if I try to raise or lower the window. Anyone ever have this problem?

Thanks,
Rob
1980SC