Thank you for sharing your obvervations! It looks like there's indeed a setup-specific memory leak caused by some kind of erroneous loop inside the server. My first try would be to disable the VNC server option "Use Desktop duplication" engine since this already solved issues in other RDP environments. Alternatively you could try installing an external VNC server, make it listen on localhost only, configure a password and configure Veyon to use that external VNC server instead of the builtin one. Last but not least: try the latest 4.5.0 release since there have been updates to all components, including the builtin UltraVNC server.