I posted this several months ago with no resolution and now that the latest beta works with CAN gps on v2 I thought i would stir the pot again. I loaded the PX4 stack on the pixracer and uavcan gps works great, back to APM and no communication. I have been using zubax uavcan gps on all of my multirotors since they were first released and have had excellent results. I have also always had issues with APM UAVCAN protocol. The issues have always eventually been resolved but it seems that too few of us use CAN bus devices.