Heartbeat only when i start companion Pi and Pilot at the same time

Hi,
i have a Boat with a Raspberry Pi where MAVProxy and dronekit is installed.
When im not starting the Pi and the Autopilot at the same time i get not Heartbeat from it and so i cant connect.
Is there anything i can do?

Thanks and regards

No source file or test is named. Start by reproducing the Raspberry Pi and autopilot startup-order scenario with MAVProxy and DroneKit, then trace how the connection waits for and receives MAVLink heartbeats. Done means a heartbeat is received when the Pi and autopilot start at different times.

Written by the indexing model from the issue text.