Hello again,
while trying to find a solution elsewhere (I already checked the postings in this forum regarding the error code 2147220970). I found that in some cases this problem is related to issues with workflows and the asyncservice related to a too high number of workflows.
As a first measure I reduced the number of completed workflows from 100.000 to 10.000 (We now delete all Workflows older than 1 month). This didn't change anything.
I would really apreciate your advice.
Kind regards,
Matteo Ostermeier