This issue has plagued me since P3Dv5 scenery's from AS/Simwings started to be released whereby replacing the default CTRL-J jetways led to several of them floating in the sky.
So far I have only checked this for LIMC.
The jetways had been configured using the GSX control panel to compile an exclude file for the scenery jetways. So far all is good, jetways removed then the GSX replacements added. Upon reloading the scenery however a number of the jetways are then in the sky.
It never occured to me that the problem may lie with the exclusion. However I decided to remove the jetways from the afcad totally, removed the GSX exclusions and now the GSX jetways load as configured at ground level.
Just to prove the point I replaced the afcad with the original once more, created an exclusion file using the GSX control panel and reloaded the sim once more, back to floating jetways.
Hopefully this indicates where an issue occurs.