Bronica 135W back problem

I've got one of those backs and I've got following problem. If I'm winding my film slowly and carefully, everything is ok. When I wind it normally, I'm getting overlaping frames. I looked inside and I found that takeup spool isn't truly connected to the gears but there is some friction that should ensure proper film winding while protecting film from ripping it from film casette. In my back, the friction isn't strong enough and it sometimes slips when winding too fast. Is there any way to increase this friction?

I doubt there is any good bronica repairman here in czech and sending it for repair somewhere alse wouldn't make sense as buying new back would be probably cheaper than having this one repaired.

I've found the 135W back to be the single most fumbly and finicky piece of camera equipment I own. Every time I use it I have to learn film loading all over again - get it slightly wrong, and it doesn't work.

There's quite a lot of variation between different films - I'm having the same problem with my Bessa-L with some films. So far I'm solving it by avoiding EFKE 25...