I've had my trigger winder for four years, serial numbered just over 1200, originally fitted to my Bessa-T. It was sort of a nostalgic purchase, as I recalled liking that feature of a Canon VT Deluxe I used in the 60's.
Of course I had to see how fast a shoot-wind sequence I could manage, and got out of synch enough to temporarily jam the shutter and cause some frame overlaps on the film.
It has three main attributes for me: First, it makes it easier to wind-on while keeping my eye at the viewfinder. Second, I like its side-grip. Third, I very much like its two strap lugs allowing vertical carry. With it over the right shoulder, it's a natural quick grasp of the grip with the right hand to bring it up smoothly to eye level. I no longer think of it as a quick winder, just a different and more convenient winder. Actually, I often forget, out of habit, to use the trigger to wind!
When I put it on the new R4A I noticed right away in the first few rolls that I was getting an average of one overlapping frame-pair every 12 frames or so. I was not using the trigger to wind at all, just using the camera's regular wind lever in my usual methodical way.
I had concluded there was something wrong with the R4A film transport when it occurred to me to remove the trigger winder and try again. A couple rolls without the winder showed no frame overlaps at all.
Now in experimental mode for sure, I put the trigger winder back on, taped up the camera's film-wind lever to prevent my using it, and shot a couple rolls while advancing film using only the winder's trigger. No frame overlapping, worked perfectly.
I haven't used my Bessa-T very much, but I remembered I had an un-processed roll from that camera+winder... After processing the 24-exp roll I noted one pair of frames partly overlapped. So it wasn't just the R4A alone suffering the problem; the T had it too (winding with the camera's wind lever).
Now I propose the trigger winder's coupling to the camera is adding a little drag to the winding process when using the regular film advance lever. Maybe under this usage the belt drive builds up a little tension that occasionally results in an incomplete advance of the film.
And, since I like the trigger winder for its other attributes, I think I'll leave it on the camera, and make sure to actually use the trigger to wind the film. This seems to be working fine, even if the winder mechanism could use a lube job...
Wondering if anyone else can report similar behavior with their winder?