Then the monitor cannot sync to the video module

Tip: if the nav picture is stable, then the monitor and wiring from video module to monitor is all OK. The problem is likely inside the video module.

There are 2 ways:

1. An external device fitted to the loom right beside the video module that blocks the speed signal, or

2. The video module has its setting changes to allow TV in motion (simplest way)

If you see not obvious external device plugged into the video module, then your video module must simply be set for TV in motion.

It's a setting inside the video module.

It's in the video module menu, but you cannot see it because of the rolling screen. But this is not the issue.

Time to try another video module (friend, wrecker, etc)