In your case the antenna mast is lilkely simply binding before it fully retracts and the motor is kicking out same as if it reached full end of travel.

The mast likely just needs cleaning and lubrication unless it's either slightly bent or kinked. The Volvo procedure I once saw in a routine service TSB is to run the antenna up and down a number of times wiping the mast with WD-40. WD-40 is a good cleaner and leaves a minimal trace of lubrication to start attracting dirt again.

Other options people use for mast cleaning are in the FAQ here.
https://www.brickboard.com/FAQ/700-900/RadioAntenna.htm#Antenna_Wont_Retract

If your mast happens to be damaged then replacement masts are available from a number of online suppliers. FYI, the other common antenna failure is the plastic geared tail breaking inside the gear housing. In that case the mast either won't fully extend or won't start to retract. Often there will a remnant of the broken tail inside the gearcase. A new mast may then not able to fully retract. Compare the lengths of the new and old mast tails. Opening up the base of the mast for cleanout isn't that hard to do and also allows you to make sure there is nothing blocking the drain.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now