I just wanted to make to post to help those with this issue.  It is regarding the Matek VTX.  If you are planning to use Betaflight 3.3, there is a glitch that causes the VTX to power cycle every 10 sec.  You will loose video for a split second.  I started a github issue.
https://github.com/betaflight/betaflight/issues/4917

The workaround is to only pick power setting 25, 200 or 400.  Picking 100 or 600 will cause the cycles.

Or go back to 3.2.3 until either Matek or the Betaflight team release a permanent solution.

Of course, the higher level suggestion is: "If you want minimal problems, don't run unreleased, development versions of Betaflight. It is expected to have problems as it's still in development."

As a Matek VTX user, thanks for the heads up Voodoo.