weird problem with 'win' key

[Andriy Gapon]

I have a pretty weird problem with the 'Windows' key in KDE / plasma5.
This is a fresh installation with pretty much a default configuration.
I do not think that I have seen such a problem before.
Also, using other window managers / desktop environments I do not see the same
problem.

So, the problem is that almost none of keyboard shortcuts that use the Win key,
whether standard or custom, actually work.  The only shortcut that works is
pressing the Win key alone to get the plasma launcher menu.  Other shortcuts
like, for example, Win+L simply do not work.
If I enter that shortcut while konsole is active, then 'sl' ('s' and 'l') gets
entered.  The same applies to any Win+letter combination, there is 's' and then
the letter.
When I create a custom shortcut with 'Win' key, it gets recognized as Meta
(e.g., Win+P is recognized by KDE as Meta+P).

xev shows the same thing regardless of WM / DE, so the problem should not be at
the Xorg level.  E.g., Win+L:
KeyPress event, serial 40, synthetic NO, window 0x3e00001,
    root 0x6a8, subw 0x0, time 5628095, (1177,395), root:(1177,432),
    state 0x0, keycode 133 (keysym 0xffeb, Super_L), same_screen YES,
    XLookupString gives 0 bytes:
    XmbLookupString gives 0 bytes:
    XFilterEvent returns: False

KeyPress event, serial 40, synthetic NO, window 0x3e00001,
    root 0x6a8, subw 0x0, time 5628414, (1177,395), root:(1177,432),
    state 0x40, keycode 46 (keysym 0x6c, l), same_screen YES,
    XLookupString gives 1 bytes: (6c) "l"
    XmbLookupString gives 1 bytes: (6c) "l"
    XFilterEvent returns: False

KeyRelease event, serial 40, synthetic NO, window 0x3e00001,
    root 0x6a8, subw 0x0, time 5628514, (1177,395), root:(1177,432),
    state 0x40, keycode 46 (keysym 0x6c, l), same_screen YES,
    XLookupString gives 1 bytes: (6c) "l"
    XFilterEvent returns: False

KeyRelease event, serial 40, synthetic NO, window 0x3e00001,
    root 0x6a8, subw 0x0, time 5628660, (1177,395), root:(1177,432),
    state 0x40, keycode 133 (keysym 0xffeb, Super_L), same_screen YES,
    XLookupString gives 0 bytes:
    XFilterEvent returns: False

I do not see anything suspicious here. Both keys are correct, the state gets
modified while Win is pressed, etc.

If anyone has seen this or has any suggestions and ideas, please let me know.
Thank you!
-- 
Andriy Gapon