@aardum: You hit the nail right on the head. Indeed, there were still some references to 3rd party print processors (hpcpp170 from the HP UPD, see member ‘hardcrack’ earlier in this thread) in the users’ terminal server profiles. I’ve changed these to winprint.
By the way: even though the user’s default/primary printer is using winprint, they still can’t print PDF documents to it if the problem occurs.
The print server is, just as the RD server, running Windows Server 2012 R2.
We will evaluate the situation in a couple of days and let you know the results.
Off topic: member ‘idtent44’ mentioned the ‘duplicating printers’ issue. We are also experiencing this. I wonder if the two problems are related.