spacedesk mouse can always be stuck due to network dropouts (better network connection -> less dropouts).
In addition to this, there are situations when after being stuck first, the remoted mouse is still trailing.
The reason: spacedesk mouse remoting network protocol is still lacking flow control.
Fix is not expected any time soon (development is currently busy with higher prioritized issues and topics).
Thus the only quick fix: Improve network performance and eliminate router. Routers always cause lags and hangs. Performance always improves when routers are circiumvented (either by connecting through WiFi-Hotspot or direct cable connection).