I had the same problem. Ultimately, the plastic drive "strip" attached to the radio antenna snapped right above the drive gear, internal to the power antenna assembly.
I have a feeling your antenna is getting ready to do the same thing.

When I fixed mine, I took my dead antenna and fabricated a "plug" that for all intensive purposes, looks like a properly retracted antenna from outside. [I still get decent AM reception, for traffic emergencies.][ I hardly ever listen to radio]

In the long run, I'll either do an S2K antenna conversion, or have the hole shaved and filled when I touch up the paintwork in a few years. h: