If I enable capslock on my US keyboard layout Thinkpad X1 Carbon, the "v" key becomes inoperable; nothing happens when I press it until I disable capslock.
Here's the output of xev
when capslock is disabled:
KeyPress event, serial 38, synthetic NO, window 0x5a00001,
root 0x19f, subw 0x0, time 147956195, (90,106), root:(1281,753),
state 0x0, keycode 55 (keysym 0x76, v), same_screen YES,
XLookupString gives 1 bytes: (76) "v"
XmbLookupString gives 1 bytes: (76) "v"
XFilterEvent returns: False
KeyRelease event, serial 38, synthetic NO, window 0x5a00001,
root 0x19f, subw 0x0, time 147956282, (90,106), root:(1281,753),
state 0x0, keycode 55 (keysym 0x76, v), same_screen YES,
XLookupString gives 1 bytes: (76) "v"
XFilterEvent returns: False
Normal. With capslock enabled:
FocusOut event, serial 38, synthetic NO, window 0x5a00001,
mode NotifyGrab, detail NotifyAncestor
FocusOut event, serial 38, synthetic NO, window 0x5a00001,
mode NotifyUngrab, detail NotifyPointer
FocusIn event, serial 38, synthetic NO, window 0x5a00001,
mode NotifyUngrab, detail NotifyAncestor
KeymapNotify event, serial 38, synthetic NO, window 0x0,
keys: 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Notably, this happens only in X. If I drop out of X11 to a regular terminal (alt+shift+F2, or similar), "V" is normal with capslock enabled, so it's something weird happening in X11 or Pantheon.