I’m using MRemoteNG to manage and create my RDP connections. In the last months, every now and then, I was unable to connect RDP sessions. When using mstsc.exe instead the RDP connection was established correctly.
After some research I found the reported mRemoteNG Bug - https://mremoteng.atlassian.net/browse/MR-582 . In the Comments somebody suggested to add the /LARGEADDRESSAWARE flag to the mremoteng.exe binary. Tried it, fixed it!
It seems that every comparable Software like ASG/Visionapp Remote Desktop, Microsoft Remote Desktop Conection Manger (RDCMan) had the same issue in older versions.