3 out of 4 screens go blank on video wall

When we plug specific devices into our video wall, 3/4 of the screens turn black - but only after a delay of a few seconds, leaving only the top-left screen turned on and showing content. The video of this happening is available here:
This happens with a Fire TV stick and a Roku TV box, but not with a laptop connected directly.
It's worth noting that we have a video switcher before the TVs which allows switching between different outputs - so this could have some effect on it, but we've done some testing and if we plug the Fire TV stick or Roku TV box (the two devices which are exerting broken behaviour) into the port where the laptop plugs in directly through HDMI, then they still don't work. The switcher we are using is this one:

After some investigation it doesn't appear to be a problem with the switcher, as the behaviour is roughly the same when bypassing the switcher completely and plugging directly to the TVs

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Clarification Request
So you are saying that a normal TV doesn't work?

If so the problem is with the stick, box or the TV.

I did find someone with a 50 foot HDMI cable and that was their issue.

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Normal TV does work

If I plug in the fire stick, or the Roku TV box into a regular TV, it works absolutely fine - it's just when I plug it into this video wall that it only shows up on 1 quarter of the screens.

There's a possibility that the HDMI cable is quite large - so I'll see if I can check that out! Might be difficult though since it's inside a wall...

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I hope you meant long...

The max distance I will tolerate on commercial (read "high reliability") is about 20 feet. Any more and I won't stand behind the install. No warranty.

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Check the cable...

So I'll check out the cable at some point - but would a 20+ foot cable cause the issue that I'm seeing? - I'm not so sure.

Considering it works perfectly fine with a laptop connected, but not with a Now TV or Fire TV stick then, I don't see how it could be a cable that could affect something like that - I was thinking the issue was more along the lines of software on the Fire TV stick and Roku TV box, and compatibility with the layout of the screens.

(I will still investigate the cable though - it was done by a contractor so I'll have to contact them)

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I was writing broadly and sharing.

Our office has setup video walls and over the years learned to put limits on areas that cause issue. 20 feet or 3 or so meters seems to be where we see rock solid never get a call about it not working so we stick to that. Past that and we look at long distance HDMI solutions.

This can irk those that point to 50 foot HDMI cables working but for us that's not good enough as our clients demand more than the one off "it works when we set it up" system. If you want reliable you don't push the limits.

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