It seems both of you have problems with the Restart, since this is what will happen when you switch airplane, reset the parking position or rebuild the airport cache.
Of course, I cannot reproduce the problem (if it was a reproducible problem, we would fixed it already), so it surely caused by some interference by another software, which might or might not be related to flightsim. Yes, of course the program will always says "it's the antivirus", because 99% of the times Couatl is not running, it IS the antivirus but that's only the most common cause, not the only one.
In order to check if the problem MIGHT be caused by a conflict with another addon, the first thing to try is:
- Is this happening only with some airplanes ? Does it happen when starting the sim with a default airplane and switching to another default airplane ?
- Are you able to test with no other addons running ? If you have proper P3D addons that install in the proper P3D way, you can disable them very easily, by unchecking them in the Options->Add-On menu. Try to disable everything in the Add-ons menu, and see if you can see an improvement in the ability to Restart.
However, you might have some legacy addons that installs in the old way, which would instead require editing the DLL.XML and/or the EXE.XML files to be disabled.
There might be a conflict we are not aware of so, testing with no other addons is the first thing to try.