09:20:42.611 gprs.c:863 pri_activate_callback
Activating context failed with error: Unknown error type
Looking at that line, we are sending a reply right after printing the
message. In case the message is NULL, you'd most likely crash inside
D-Bus or get an assertion of some kind.
The pending variable is also not messed with anywhere else, so you
should be getting a reply.
The only thing I can suggest is to try and simulate this behavior with
phonesim and see if you can duplicate / debug it.