the jetways stand around alone and the planes from "My Traffic professional" go through buildings etc.
That's very simple: the AFCAD that comes with My Traffic have created this conflict, so FSX use them instead of the ones from FSDT. Those additional AFCADs should be used ONLY with default airports, but must be removed if you have ad add-on airport.
Use the free FSX Airport Scanner tool to search for AFCAD duplicates and remove them. If that tool can't find them, search the My Traffic folder with .BGLs, and remove all that have a matching ICAO/Name related to your FSDT airports.
Other airports I have, don't seem to have this problem!
Because such conflict will only appear if the airport includes certains elements, like animated jetways and/or special effects, if the other airports you have don't have any of this, they won't be affected.