vehicle.commands.downloads timeout

[eminakgun]

I process as the steps,

1. clear out the mission
   vehicle.commands.clear()
vehicle.commands.upload()
2. I upload a mission from GCS
3. Read the uploaded mission

vehicle.commands.download()
vehicle.commands.wait_ready()

When called wait_ready(), it gets stuck sometimes. So I can not proceed. This issue tend to be more likely when number of waypoints are increased.
I am running ArduPlane 3.9.11 and dronekit 2.9.2. It might be related to Plane version maybe?

[eminakgun]

Here what I found in the codebase indicating a fix related to downlaod method.
https://github.com/dronekit/dronekit-python/blob/master/dronekit/__init__.py#L2964
# BIG FIXME - wait for full wpt download before allowing any of the accessors to work
Can somebody explain what is meant here? Maybe I can figure out the solution and give a PR.

Btw I tried with Plane 4.0.5 firmware and looks fine tho. No errors. Maybe there are something mismatching MAVLink mission protocol or implemented differently. Any ideas?

[eminakgun]

I re-implemented and tested the mission download protocol properly. #1039