Not sure if this will help someone but i reckon I will not be the only one to have found this problem. simply put, my drivers belt when accidently pulled out to the limit, sticks and will not return, sometimes a few tugs released it and others it stayed put for several days , until of course it refused for ever. I removed the hood clips,tray and soundproofing, expecting to remove it and replace it .
Though I found a plastic cover which I guess keeps dust and muck off the belt as it is reeling in and out, photo 1 this is not fixed but the belt runs through it and is kept more or less in place the shape of it and the two dimples on the reelbody, however mine seemed to have worn and slipped past this point down over the torx bolt that fixes the reel in place.photo2 This is where the cover sits and gets stuck stopping the inertia action.
The fix is to put a small zip tie through the higher of the two sets of drilled holes in the reel body, leave it slightly loose, it does not foul the belt but prevents the cover drifting down to problem area photo 3. I will attach some photos.
amazing things zip ties.