This all started with me trying to get 2-finger scroll working. In Windows, I got used to it. So I found a thread that said to run these commands:

synclient VertTwoFingerScroll=1
synclient HorizTwoFingerScroll=1
synclient EmulateTwoFingerMinW=5
synclient EmulateTwoFingerMinZ=48


It kinda worked, when I put one finger extremely close to the other. So another thread said to fine-tune the MinW and MinZ by doing synclient -m 150, where I got the error "Can't access shared memory area. SHMConfig disabled?"

So I set off to enable SHM Config. I found another post that said to edit my /etc/X11/xorg.conf file and add Option "SHMConfig" "on" - so that's in there, and I still get that error. My mouse is all over the place almost any time I touch it at this point!

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I added the following line to /etc/profile and now it works. May be you could try that.
xinput set-int-prop "SynPS/2 Synaptics TouchPad" "Synaptics Two-Finger Pressure" 32 40