Hi Christian,
before Umberto chimes in here, I thought I'd point out that in my experience sometimes glitches like the one you're describing actually has something to do with the underlying airport afcad rather than GSX.
eg: there are a couple of gates and one gate in particular at ORBX YMML (Melbourne, Australia) whereby the underlying afcad is so messed up that the GSX pushback spins
around like crazy for a moment.
If you can do it, open the airport afcad with an appropriate program and take a look, this may unlock this mystery.
Of course, if you provide the details of LEBL (ie default or 3rd party) someone else can verify this.
Rgds,
Steve