Oh, just after replying to this thread I managed to get my installation working again.
The problem was that due to scaling problems I followed this FAQ and set the two environment variables to the following (note the 0.9 in the second line):
export QT_AUTO_SCREEN_SCALE_FACTOR=0
export QT_SCREEN_SCALE_FACTORS="0.9;1"
After changing it to the following it worked again perfectly:
export QT_AUTO_SCREEN_SCALE_FACTOR=0
export QT_SCREEN_SCALE_FACTORS="1;1.5"
I find it quite bizarre since it has been working fine for half a year, maybe it had to do with some QT update.
