For the 3rd time: Yes, it's still the same...
That's the 1st time you finally replied that you are now having the ORIGINAL "Overflow" message. Your subsequent messages after the first one show entirely different issues, which were clearly a result of your editing (the reversed doors was obviously a entirely different thing, and sure it didn't caused an overflow error) and you never said you are now back to the original "Overflow" error.
About the "Overflow" error, you have been answered about it already, and it doesn't have anything to do with the difference between P3D or FSX, NOBODY has ever reported THIS problem before, and we don't have the slightest idea what is causing, other than it's surely an external cause, such as external program (even not related to flight simulation) that is interfering.
We had reports of unusual situations such as power management programs or video card tweakers causing problems, but this (the "Overflow" error) is the FIRST and ONLY report of such specific error.
The only possible solution, is to proceed by exclusion, and trying to quit all running programs one at time, until you find the culprit.
And explain me what you do on my system, mentioning KLAX and XPOI!
The problem with KLAX is caused by a free scenery from Ray Smith you have installed, that by unfortunate chance has a file with exactly the same name ( KLAX_OBJ.BGL ) and a very similar size to one of the KLAX files, so the Addon Manager believes KLAX is installed, but "outdated", because that file is not what is expect it to be.
You can fix this by simply renaming that file to anything you like, provided it keeps the .BGL extension.
Not that this has anything to do with your "Overflow" problem, the only result it will cause a bogus "Trial for fsdreamteam KLAX V2 has started" message.
What about XPOI ?