7 speed XT strange shifting

[RadNomad]

1993 era 7 speed Deore XT and i’m pretty sure the set up is as per original (ST-M095 shifter and RD-M735 derailleur). Shifting across a 7 speed cassette should take 6 ‘clicks’ of the shifter, but curiously the derailleur achieves it with only 5 clicks. The shifter has a 6th click but it seems redundent. This occurs both up and down the cassette. Each click of the shifter takes the derailleur slightly too far, so by moving across 6 sprockets with 5 clicks i always end up with skipping gears no matter how much adjusting i do. I’ve played with basic cable tension, H and L screws, barrel adjusters, but nothing solves it.
The cassette is a new genuine and correct HG50 7 speed and the chain is new Shimano HG 7 speed but the problem was there before so i’m satisfied it isn’t a cassette/chain issue.
I’m now concluding the XT shifter mechanism must be worn such that it pulls or releases too much cable per click. I find this surprising as i’ve never encountered such a phenomenon before, but i can’t find any other cause.
The derailleur itself may have some wear but it’s pretty good and pivot clearances etc don’t feel different to others i’ve used that shifted nicely, it isn’t knackered.
Anyone had similar experience?
I did have another bike with this exact type of XT shifter and it packed up, so i’m doubting the durability of this generation of shifter..
Bike is the Marin in my sig..

 

[krakhaus]

Re:

Sometimes push button shifters get gummed up inside so they don't really like to fall into place. Try spraying it out with WD-40 or degreaser. I was having issues with a XTR front shifter, and that solved it.