Had the issue with Mrs R's 307 drivers side. Slower than a slow thing & got shut in door a couple of times as a result.
Bit of googling & tried giving it a clean which did improve matters slightly but not to any great degree.
Decided to give the 'silicone spray' suggestions a try as the alternative was to replace the belt.
Used '3-in-one' silicone spray.
Pull belt out fully & spray both sides.
Allow to retract then work in & out a few times.
The spray dries quickly & doesn't stain clothes when wearing the belt.
Now works completely as normal.
Bit of googling & tried giving it a clean which did improve matters slightly but not to any great degree.
Decided to give the 'silicone spray' suggestions a try as the alternative was to replace the belt.
Used '3-in-one' silicone spray.
Pull belt out fully & spray both sides.
Allow to retract then work in & out a few times.
The spray dries quickly & doesn't stain clothes when wearing the belt.
Now works completely as normal.