Created attachment 9067 A patch to fix the issue We found out, that parole will not honor the Volume Up/Down or Mute-Toggle don't work when the player is set into fullscreen. We fixed that by re-working the way keys are actually handled in Parole (went from the glade embedded handler to code). I'm upstreaming a couple of patches while traveling, so this might also be done by https://git.xfce.org/apps/parole/commit/?h=bluesabre/gtk3&id=319707d65b26d960916a68226b28f351035724a9 but I can't test right now
Markus Ongyerth referenced this bugreport in commit 18bbdccbc36863273db8042dc18a079bc0208795 Fix volume hotkeys in fullscreen (Bug #16005) https://git.xfce.org/apps/parole/commit?id=18bbdccbc36863273db8042dc18a079bc0208795
Not sure why it didn't work the glade way, but thanks for the fix!