Please be more clear with your reports. Since I cannot replicate ANY of these, you must be more precise, otherwise we'll never be able to find the problem.
When you say "the pushback truck disappeared", it doesn't meany anything. Does it mean:
1) The pushback tug never appeared to begin with when you selected a parking ? If this case, please ALWAYS include ALL the following data: the airport used, the gate used, the plane used and, possibly, the operator selected
OR
2) The pushback truck appeared, but it disappeared after doing some operation. In this case, clearly indicate the GSX operations you called and, possibly, in which order. Adding ALL the previous information from #1 about the airport, the plane, the gate.
OR
3) You started pushback, and the truck disappeared while pushing back.
