36 minutes ago, SteveW said:

Yes, we have to be careful. As it happens I never worked out what the problem was causing the sim to stay running, thanks for that.

The issue in some cases is, that some add-ons need that P3D is started with administrator rights. This is not related to the SIM but on how Microsoft want´s to prevent "WIN 10" from abuse by hostile software. Because the, how MS called it, productivity tools, like the auto-last appin use-start- after login, will not start an app with adminrights, you get into trouble with the "normal" privileged SIM and add-ons. Though you can get rid off all that, because we don´t want to be productive and safety is overrated anyway

Edited October 14, 20205 yr by BerndB

Admin problems are mainly due to addons installed into the simulator program files folder that want to save settings there. Instead of running as admin you can add the Modify Allow permission to the Users group on the LM or P3D folder: Explorer, Properties, Security, Edit, choose Users group, check Modify Allow. After that you can run P3D safely without admin rights, and a bonus is you can edit aircraft.cfg files and so on, with Notepad, only authenticated users are members of the Users group.

In my experience, this can be caused by a P3D or FSX addon that does not close with the simulator. My theory is that Windows detects that there are files in use inside the P3D or FSX folder and restarts the simulator, despite the fact that those files are not in fact P3D at all but an open addon.