The bug appeared to me after updating konsole to KDE Frameworks 5.6.0. I'm using packages from ArchLinux repos. Reproducible: Always Steps to Reproduce: 1. setxkbmap -layout us,ru -option grp:caps_toggle,grp_led:caps 2. Press CapsLock to change the layout 3. Press any key Actual Results: The first keystroke after changing the layout is going to be ignored, even keys like backspace or return. Any subsequent keystrokes are being handled properly (until you change the layout again).
Reopen if you can still reproduce this issue.