happen with every plane - here the TRuth A306 ->http://prntscr.com/gx47k0
The problem doesn't happen here, and we tested it precisely with that airplane. We have added an internal configuration in GSX for that plane in this release, for the precise reason that it works perfectly with the KSDF Cargo Stand.
As I've said, if you customized it before, because the previous GSX didn't included it, try to Reset the configuration to undo all your settings and return to the customization that comes with GSX.
See the cargo being loaded with no errors, with the Thomas Ruth A306 plane, same gate as your report (Ramp 3S - Cargo Stand C4) in the attached screenshot