Andersen sliding patio door height adjustment not sticking
I have a 20-year-old Andersen sliding patio door.
It got roughed up this weekend, and is no longer aligned. It slides fine, but when the top edge touches the door frame, the bottom edge is almost half an inch shy of mating up.
I know this is supposed to be as simple a matter of either raising the corner of the door closest to the frame where it closes, or lowering the corner of the door farthest from the frame.
But the rollers I try to lower, won't, and the rollers I try to raise DO raise into alignment, but then drop back down the moment I remove the screwdriver.
I've removed the door (several times). I've looked at the rollers with the door removed and they appear to be aligned, at least to the eye. Obviously they're not.
When I look into the alignment holes, I don't see a screw, per se. There is a hole, with slots on either side, and my screwdriver seems to fit into the hole, even though only one of the two allows me to turn. Is this what I'm supposed to be seeing?
What other suggestions can be offered? This is something that's supposed to take 30 seconds, and I have used a lot of my weekend trying and failing to adjust the door. Again, it slides fine. But it doesn't come anywhere close to closing flushly against the door frame.