Cannot click anymore

Since a while I notice some strange behaviour of MuseScore. I am using musescore-2.0.3-2 on Arch Linux and after working a while I'll try to click on another window than MuseScore but I cannot click anymore. The mouse moves, but I cannot click any item anywhere, neither on MuseScore nor anywhere else.

After exiting MuseScore (using the keyboard / shortcut), it works well again.