Happened to me the first time this season. Maybe the plastic threads for your set screw are sloppy and it's time for a new handle....they are $5 on Amazon or you can call your dealer and see if they will replace it under warranty. Remember to lube the antenna gears so there is less resistance when you crank up the antenna.
2013 26BH ghetto model w/ 4 plain rims and some rust
2001 Silverado 2500HD 6.0 gasser
I have a fever...and the only cure is more camping!