UPDATE (February 23, 11:30 a.m.):
The systems are running stably again (provided no further hardware defects occur).

Due to hardware problems with the central storage system, occasional disruptions to central services occurred from late Sunday afternoon onwards.
The cause of the problem could be narrowed down during the course of the evening. The systems have been provisionally stabilized.
A detailed analysis and any further work required can only be carried out from Monday morning onwards.