In my test case, I have DRZewiecki Chicago Landmarks loaded.
With all duplicates removed (see below images), I am able to launch a flight out of FSDreamteams KORD fine
Install Asobos version of LEMD which is now a duplicate of LVFRs LEMD, CTD from the Fly button.
Remove Asobos LEMD, all is good again
Install Asobos EDDS which is a duplicate of Justsims EDDS, CTD at the Fly button
The same happens for duplicates from Simnord, ORBX, FSDreamteam, etc. The developer of the “duplicate” does not matter. The existence of a duplicate in Content Manager does
So you might say “it’s because you are flying out a payware airport”
So I repeat the process for KMDW Chicago Midway, which is a default airport. Same CTDs result
So now you may say, it’s a problem with Chicago itself. No, I can do it other places like London, but Chicago happens to work well for all these test cases
So now I try flying out of KPWK Chicago Executive (this is default still). I can fly. I can fly all around Chicago no problem at all.
So now I install the Chicsgo Enhanced night lighting mod by Dreamscenery. Can’t fly from KORD or KMDW. I can fly from KPWK, and fly around Chicsgo at night with the additional enhanced lighting, and it is truly spectacular.
So maker of the addon does not matter. This happens at payware and default airports. It is like I said, when attempting to read the Content Manager list to see what mods will be in effect for the flight, if a duplicate is encountered during the read, it results in a CTD. This is clearly a sim bug.
The bad thing is, we just had a sale of airports for Xmas and New Years. Lots of people bought airports during the sale, and all over Facebook people are saying “Don’t buy Justsim”, “Don’t buy ORBX”. It isn’t the developers faults. It’s a simple bug. But one that needs to be fixed.