Just recently my seatbelts have become slower and slower to retract when undone

I've heard this is due to the belt becoming slightly worn
The fabric becomes 'fuzzy' making it difficult for the belt to retract

Is there anything that can be put on the belts in order to make them 'smooth' again?

 

Not sure about the fuzz but have had the retracting springs losing tension over the years causing your issue. Not in a Porsche though, my wife's fx35 grocery getter is starting to have the issue. I keep closing the belt in the door. So annoying.

 

the driver's side seatbelt on my 2003TT is slow to retract but the fabric shows no sign of wear. I have assumed that the retraction mechanism module would require replacement. for now, I'll deal with manually coaxing it into place. my other cars have a similar issue to different extents.

 

I have the same problem - think CPO will cover it