UI:
  - #5422 [FIXED] : testing an activity - display message takes 9-12 sec. to disappear

  - #5423 [FIXED] : "Ansicht aktualisieren" takes 11-12 sec, no status/progress bar, system seems to "freeze"

  - #5813 [FIXED] : interface did not update after room assignment

  - #5861 [FIXED] : if the audio to be played has unknown length, "Restart previous music once finished" must be disabled

  - #5881, #5872, #5873 [FIXED] : Shorten text in volume column

QUALITY LEVEL:
  - Only functional testing performed - verified above fixes