Interesting, the installation is a bit more complicated and likely had a previous system before the Go!Control as the WS4945NA is a DSC sensor. There would be a wireless translator somewhere on site.
The WS4945NA would just be acting as a transmitter for a wired sensor from your description, and the WS4945NA has two tampers. One is the standard cover tamper, the other is a wall tamper which may or may not have been used. This installation manual shows the two tamper switches.
If programming has not been changed this is likely just a physical issue. Over time the wall tamper may have loosened and is the more likely culprit. Can you check to make sure the wall tamper or cover tamper switches are not damaged, and that the wall tamper has not made a depression into the wall behind it. If it has it may be deep enough to release the tamper switch.