Fussy HDMI inputs on ATEM Mini Pro

I'm currently hiring an ATEM Mini Pro with a view to buying the ISO variant when it is back in stock.

This morning we had nightmares trying to get two cameras connected: Fuji X-T2 and Sony A6000. Whichever camera was connected first worked. The second camera connected did not (Fuji or Sony but not both together). In the end, we gave up and went for an ancient Panasonic videocam as the second camera.

After the event, I did some experimenting. I tried using a cheap (GBP12) HDMI splitter to buffer the second camera (Sony), with a short lead to the ATEM, and it worked! I have since found that someone on YouTube (video watch?v=ZWJSc6Gb35Y) has the EXACT same solution.

What workarounds are others using?

Why can't ATEM use less fussy HDMI inputs on the ATEM Minis? Are they trying to push their own cameras? Would a less fussy input be detrimental to other sources? Perhaps the could provide a fussy / not fussy switch on each channel? I'd certainly pay extra for that (as it looks like I will have to anyway).

We are using a GoPro Hero 7 camera.. had to drop to 720p from 1080p due to the connection (HDMI from camera to sending unit connected to cat5 or cat6, then to a receiving unit and HDMI to mini pro). Other issue with GoPro is “stabilization” has to be off as there was a huge delay between voice and video.

My point is, check different camera settings. You might be surprised what will work.

We are using a GoPro Hero 7 camera.. had to drop to 720p from 1080p due to the connection (HDMI from camera to sending unit connected to cat5 or cat6, then to a receiving unit and HDMI to mini pro). Other issue with GoPro is “stabilization” has to be off as there was a huge delay between voice and video.

My point is, check different camera settings. You might be surprised what will work.

Yes indeed. But this does seem to be signal related. I can run both cameras at 1080P25 (probably higher, but this is the minimum I've tested, and the lowest I want to go) with short HDMI leads. When I add some distance (e.g. 10m), the ATEM Mini Pro's HDMI inputs only cope with one camera, until I add a $15 unbranded HDMI repeater. So, the question remains: why can't the ATEM Mini Pro be as forgiving?