Hi!
Thank you for your input, but unfortunately this doesn't seems to be te problem.
The hotfixes are not applicable for our Server 2008R2 machines. Also the Windows 10 update is already installed.
The register keys are also there, if a client is having issues restarting the printerspooler fixes the problem for a while, but the problem is comming back at a later moment.
Still having big issues here! :(