So once again getting frustrated about how often the cover tape wasn't quite pulling hard enough, I had a close look at what was happenning - I'd always assumed the main issue was the belt slipping on the tape.
However I noticed that in some cases it was actually the belt slipping on the take-up reel pulley.
I've roughed up the pulley inner surface, using a needle file mounted in my pillar drill, and this seems to have made a noticeable improvement.
(I use the orange belts from polymax, which seem to be better than the black ones)
Interesting, I might try this. I was aware that a lot of the slipping was occurring at that end.
I use the orange silicon ones mostly as I find they are a bit more grippy than the shiny black ones, though I have found they do tend to stretch over time whereas the black nitrile ones dont stretch so much but crack and snap instead.
I also wonder if a couple of tight-fitting 1mm o-rings round the pulleys might help.
Just finished a large-ish job with twenty 8mm lanes and no slips at all - roughing up the pulleys has shown a definite improvement over previous performance.
Gents, this is excellent work. Well done!