The Proper Way to Connect FPV Goggles to a Groundstation (The Goggle Module Trick)
It is a little known fact that when the internal/external switch that turns on an internal/onboard receiver module is switched to external or "off", there is still power going to the pins of the module and that may cause "bleed" of video. This can be seen randomly, often times when there is a higher powered vtx closer to the powered-off vrx in comparison to the tuned vtx.
There are two things that can be done to combat this issue.
First, if at all possible, simply remove the module entirely.
Secondly, if that is not possible, perform "the Goggle Module Trick".
1) power on the receiver module (select internal)
2) use the onboard channel buttons to advance up a channel or two, ensuring you hear a short beep each time.
3) use the onboard channel buttons to lower the channels until you hear a long beep, known as "channel zero", but may appear as channel one on the band that you are on on the module. The main entity is the long beep.
4) power off the module by switching the switch on the bottom of the goggles to external.
5) plug in the groundstation cable.
This solves the "bleed" problem 99.99% of the time.
(See this video in chinese:)