Ok, this is a issue haunting me for quite a time and I am sure I can replicate it every time I am asked to. I havent tried on many computers but my computer is running latest spacedesk driver along with most updated windows 10. I am sure this is not my graphics drier issue since its a old issue.
The issue actually is that when my serer computer has 100% cpu load, the spacedesk app crashes.. Though it is running, it does not connect via client. It connects and disconnects in half a second saying error code -0-2-5 or something. Then it does not work even after reinstall or closing the app with task manager. The only way I have found this working is reinstall the driver in server computer.
I thinkk this could easily be fixed using some minor tweaks in the code.
Side note (my time with spacedesk but worth reading once): I have been using spacedesk as my primary monitor for about 5-6 months now. My desktop is server and laptop is client and both have windows 10. I use a gigabit ethernet(a particular among a collection of 5, yes even quality between gigabit ethernet differs and matters for smoothness) (both my devices have gigabit ethernet port). I can actually play games(gtav, witcher 3, rocket league, mk10, mk11) at 720p at 60fps (though there is input lag particularly noticeable and problematic in fighting games like mk10 and mk11) but in gtav, or any non fighting/competitive it does not matter at all. And, i dont know how only some games can transfer 60fps at 768p. Also, I previously installed client in windows 8.1 which was way more laggy and not smooth. Its not my GPU problem like when I used monitor It could even run easily at 1080p 60fps.
Also, if you could give any software edit suggestion like going to device manager and tweaking values to get even better performance, it could be helpful because my full gigabit capacity is hard used every time and thus sometimes when sudden boost in resolution is made, it lags.