On Windows pressing shift with NumLock active is supposed to cancel out the effects on NumLock. So pressing e.g. 2 on the keypad should send KP_Down. This works in most browsers, but not Microsoft Edge. Tested with Edge 18 on Windows 10.
Needs retesting with new Edge.
I tested this on Microsoft Edge Version 95.0.1020.53 on Windows 10. ThinLinc server Version 4.13.0post (build 2350) on Ubuntu 20.04. The issue is no longer present. Since we are dropping old Edge support as of bug 7550, this bug can be closed.