I think the fix you need depends on how far the deterioration has gone. When it starts to drag, the "stack of washer" fix is the easiest and most effective to do - the next level is probably the bent back guide, then the slotted screw holes and finally, if the mount is peeling off the glass, a re-attachment. It can get to the point where the mount actually breaks off from the glass and will need to be replaced, or the regulator fails due to the excessive drag from the slipping window. You'll need to examine and try to simplest fixes first, then move on to the more extensive as needed.
-- John