Its very strange all of this, its as if I have to install some of your airports over and over again to make them work properly.
No, you don't. Provided, of course, you use their latest installers that supports the latest P3D versions and install the sceneries in the correct folders, depending if you use FSX, P3D or FSX:SE
AND, after we came out of Beta with Couatl 3 and GSX, if you had to reinstall any of the sceneries for any reason, and you still wanted to use previous installers, you always had to install Couatl 3 or GSX as the LAST thing you do, otherwise the old installer that came with Couatl 2 would "downgrade" the GSX/Couatl 3 install, and possibly cause a mess, that's why you had to install GSX or Couatl 3 at the end.
Instead, if you re-download all the installers now, they have all been updated to use Couatl 3, so the installation order won't matter anymore, since they all come with the same basic set of support files now.
LAX though has no improvement despite reinstalling it.
Since there wasn't any problems at KLAX to begin with (other than the crashes, which are probably unrelated to it, see my other message about trying with a DEFAULT airplane), it's just normal the reinstalling it won't show any change.
I think it could be addon manager or couatl issue, perhaps combined with anti virus I have no idea. My anti virus has been set to exclude your files, but it seems to still cause problems if its kept on and I enter your airports
If the antivirus is interfering with the executables, they won't even start, so you won't see ANY of the FSDT menus, and no scenery at all.
If the antivirus is just interfering with the opened files (without blocking the executables), you'll see a very long cache regeneration time, IF you have GSX installed AND when you update/change anything in the Scenery Library, so a cache regeneration message is displayed and, because of the antivirus, the regeneration will take a long time, so GSX won't be available until then and it's possible that some of the sceneries might not work entirely correct until the cache regeneration is completed.
Which is why, in the other thread about the latest GSX, we suggested to exclude the whole simulator root folder (assuming you keep your sceneries there), from the antivirus real-time scanning, and this will likely speed up the sim startup time, so it won't be beneficial just our products.