Though I know that this is a known problem here I want to stress it again: Using the latest GSX version I get the message
It's not a "known" problem, unless we'll assess what REALLY the problem is. Don't confuse the message with the problem, the message can be caused by many things.
As suggested in all threads discussing GSX not finding AFCADs, the first thing you should check is "Is GSX using the correct AFCAD ?". And that's why GSX is indicating the name of the AFCAD in use, when you select the customize parking position option.
THEN, after you see which AFCAD is in use, we can try to understand WHY, assuming the wrong one is used, the correct one hasn't been used instead. The Logging feature of the Troubleshooting page of the GSX - Settings menu, is also useful to know about potential issues with an AFCAD, like why it hasn't been chosen or if there are problems with it.