Mavlink stops on version 4.0> (SD Card inserted)

I have a serious problem with Ardupilot version 4.0>
I have a companion computer on the drone which sends Mavlink messages. Apparently every time I insert the sd card into the pixhawk the companion computer terminates Mavproxy/dronekit but when I remove the sd card this never happens. I never had this problem with previous versions of Ardupilot. I seriously don’t how these two are related to each other.
I have tested 4.0.0 - 4.0.2 - 4.0.3 all of them had this issue, but 3.6.9 is fine.

We run with an SDCard inserted all the time, and it works fine.

Yes, but this is not happening randomly I tested more than 10 times.
I have mavproxy and my dronkit code on start-up when I remove the SDcard everything is fine but when the SDcard is inserted the code stops running.
I know this seems weird. But there must be a conflict between these two.
I changed the firmware back to 3.6.9 and the problem disappeared.

I think the fact that I’m running everything on startup has a kind of conflict with Ardupilot version 4.0>

Also I checked the parameter LOG_BACKEND_TYPE and it was on file logging by default. Thought that might be set on mavlink logging but it wasn’t

First off, do not use 3.6.9. Update to at least 3.6.12.
Are you inserting the SD card while the FC is running?

No, before I power up the FC
3.6.9 was the stable release I think?
I mean I can’t find 3.6.12 among the stable releases
I know these two are completely unrelated. I should probably try to find the root problem which is presented in this way.

Did you look under:

I’m so sorry. My bad. Don’t know why I missed that one :slightly_frowning_face: