If the parking spot is not recognized by GSX, it would say so, wouldn't it? At least there would be no marshaller (no working VDGS) and handling vehicles at the chosen spot. Which is not the case: deboarding works perfectly, even when 'clutter vehicles' are standing around.
I will have a closer look and always try to exit Couatl, when that happens, just to check for sure if it's GSX or MSFS clutter.
Another info: it happens not always at the same airport / parking spot. So if it is MSFS clutter, it could be a simconnect thing (means: sometimes GSX is able to remove MSFS clutter, sometimes not because of some simconnect issue).
Best wishes