My first recommendation would be to delete the installation file and try to re-initialize the robot. I do remember facing a similar issue previously that was possibly to do with switching between URSim for UR3/5/10 (the controller process not being stopped before the new GUI started possibly?)… but don’t remember exactly how I fixed it unfortunately.
Is this happening every time you start URSIM? After a VM reboot too?
Might also be that some files are corrupted. Try installing new instance of URSim on VM. Download URSim for linux from our website, and install next to the one that is not working.