Update KB3172614 (July) and KB3179574 (August), seems to break rdpcorets.dll.
Microsoft is working on a update, but we still have this issue on a couple of RDS servers.
I have implemented a temporarily fix, which restarts the TermService then the black screen appears.
- Create a .bat file which have the following lines in it:
sc config TermService type= own
taskkill /FI "SERVICES eq TermService" /F
sc start TermService
- In the Event Viewer find a log which has the event ID code 4005, and create a Task Schedule for that.
- Go into Actions and find the .bat you just made and add it.
After that, your Task Schedule should restart the TermService and the users will be able to log on after that.
For me it takes about 30 seconds, then the TermService service is killed the rest of the users which is logged on will be disconnected, but not logged of.