SIYI a8 analog output setup

I am trying to figure out how to activate analog output for Siyi a8. The Siyi manual says that value 7: Set video output as CVBS for the Photo command CMD_ID:0x0C------Photo would do the job, but how do I send this command from Arducopter?

Getting more problems… I changed the output to analog using SIYI configurator.

However, if I connect the video output to the video in of Matek 743, the board does not boot, no video is output, and I cannot connect to the board using Mission Planner. When I disconnect the video output from Siyi, everything works fine.

Siyi seems to work fine, the gymbal keeps its position, and camera records HD (using autostart feature).

Any ideas about the issue with the siyi analog output preventing the board to boot?