The last tuner on the treble side was too short inside to tighten the string. Thomann gracefully sent replacement, but then there was a plastic knob (ok, mistakes happen), then they get a new one from Grover, which is working, only it is significantly shorter than the other 5 as it is barely long enought to go through the headstock wit( the string hole. Thomann (no complaints about them) are now sending me yet another tuner, and hopefully Grover has QC up and running again. The five correct tuners operate just fine, and seem stable, but it is just a shame that they are not consistent when it comes to quality.