When you park the car on top of your drive do you have a level "0 degree" parking pad or is the vehicle always parked on an incline?
Seems your transmission linkage, gears and spline is causing the transmission to pop into neutral. But I'm no expert. In addition your emergency brake appears to not be holding contributing to excessive strain on the tranny.
Since Mt. Kisco Volvo has been working on your car it's best to give them an additional call explaining your latest problem.
In addition gather all your work orders and invoices and start explaining the problem from the very beginning as when other SS members come on line they will need information in order to help out.
Use a point format in explanation along with the language written on work orders.