Originally Posted by
fietsbob
IDK, I'd have to be there. maybe it's user technique shifting under a load, etc. , stuff I cannot Guess..
some one from the shop may ride along with you to see your situation replicated..
./.
It's not a technique issue. The shifter will move free even when the bike is stationary, which usually you can't since it is actually trying to move the shifter which won't work if you aren't pedaling.
I put the bike on the stand and made a quick video to illustrate. you can hear the shifter make a small click, which almost seems like it is trying to grab the cable and doesn't. But the shifter moves freely because it isn't pulling on the cable at all.