My global keyboard shortcuts for media controller are set as follows: Action Global Global Alternate Media playback next Media Next Ctrl+Alt+PgDown Media playback previous Media Previous Ctrl+Alt+PgUp Play/Pause media playback Media Play Ctrl+Alt+Ins Stop media playback Media Stop Ctrl+Alt+End After I first log-in everything is working as should, both media keys and alternative shortcuts. Once I lock the screen and then unlock it again, both global and global alternative shortcuts stop working. This issue appeared after updating kscreenlocker to version supporting multimedia control (with Plasma 5.10), I guess it has something to do with that. Others experience the same behaviour as well: https://bbs.archlinux.org/viewtopic.php?id=226835
This seems to have been fixed already in this commit: https://phabricator.kde.org/R120:7bd909fa3a4f70bf4c03c43b025f7ed65c2e5b5c I just tried building the branch 5.10 and it's working fine for me now. I think you can mark this one as fixed.
*** This bug has been marked as a duplicate of bug 380526 ***