Strange I can’t seem to find anything out there or in these forums about this:
Starting a few weeks ago my only TS1 (at front door) started returning “invalid user code” during disarm no matter which user code I tried. Sometimes a 2nd attempt would eventually work. But now it seems no reattempts work anymore to where I have to run the 20 ft to the GC2 by the garage before the alarm trips. GC2 always disarms on first try so the codes all appear OK.
A couple months ago I removed the TS1 so my wife could paint the hallway there. Pretty sure disarm worked for at least a couple weeks after. And there are no other symptoms that would allude to a bad radio over that 20 ft span. Arming at TS1 always happens on first try. Weather and Zwave display always appears up to date. Checked 900Mhz module connectivity to GoBridge (even further away) and all passed fine.
Ideas? Yes, I pulled power on the TS1 and even unpaired then re-paired it to the GC2. No joy 
If it states invalid user code, that means that an invalid user code was physically input at the TS1. Typically this means the screen calibration is off or too much pressure is being applied, registering errant numbers instead of the intended code.
Try a test by tapping the code at the TS1 with just the very tip of your finger. Narrowing the surface being applied to the screen will typically get around the issue.
You can go into settings and perform a screen calibration:
Security > Menu > Toolbox > Master Code > Calibrate Touch Screen
<Embarrassed> I never paid attention to the (very) quick keypress feedback to realize the wrong touch point 
Just figured the codes were always being remotely read (or not at all) from the GC2 panel.
So it appears my screen now has problems because I can sometimes press '3" yet see the ‘7’ response in the opposite corner of the keypad no matter how light or heavy the press and even after re-calibration. Bummer.
This may just be a physical issue with the TS1, but something you could try is to Reset the TS1 but pressing and holding the two face buttons for 20-25 seconds. Then re-learn the TS1 into the Go!Control Panel.
Does this reset help with button recognition?
Well, the reset sorta seemed to help in that there were less missed keys as I kept arming/disarming to test. But it still well missed a couple by a good 1/2"+ off so not quite in the clear. I’ll keep watching it. Thx!