I recently bought a bicycle that came with a 7-speed microshift-M21 rear derailleur for which they have used a microSHIFT TS38 Thumb Tap Shifter. I observed that the rear gear shifting is not accurate which on further observation looks like the LOWER LEVER on the shifter is making more clicks (step increments) than it should. I believe it should make only one step of gear change on either of the lower or upper lever presses.
So what exactly I observed is that when I press the LOWER lever on the shifter to its full range (till where max it can go), it makes a total of 3 clicks (step-changes) while pressing the upper lever correctly makes only one step change.
Any idea if this is a normal behavior of these microSHIFT-TS38 Thumb Tap Shifters? I checked everything else like the cable tension and L/H screws on the derailleur which are fine. Nowhere on their website is it written as a feature that it supports more than one shift using the same lever press in extended press.