Then the parking spots might be really isolated.
If any of these scenery has jetways, have you verified the GSX replacement jetway files for them has been disabled, as they should ?
This is done automatically each time you update GSX, but if you installed a 3rd party scenery after GSX, and you don't update GSX or enter in the GSX Config Panel to Exclude 3rd party airports, the GSX jetway replacement file will cause a conflict, since these files are only supposed to be enabled for default airports.
Also, if a package doesn't follow the official Marketplace naming standard, it won't be automatically detected by GSX for jetway disabling, so you need to add its own code manually.
