Camera image cycling weirdly by itself

ATEM mini Pro (or PTZ Optics camera) is behaving strangely as every 2 minutes the image will change and come back by itself. It's not that the image goes from entry #1 to another entry on the ATEM but rather that the image from the camera changes shape. It does not do that when the ATEM is not in the chain. Has anyone ever seen such a behaviour? I'm trying to pin point the problem. I would love to show you a short video but the Forum is not letting me post one or include a url for it in this post! I honestly don't believe it is due to the camera. The camera is plugged in using an HDMI cable to port #1 of the ATEM mini Pro.
PTZ Optics 12x SDI (plugged in using HDMI)
ATEM mini Pro
Things left to try to solve the issue:
1- Change / shorten HDMI cable
2- Plug camera in each of the different HDMI entries on the ATEM
3- Try an SDI cable and Decimator-HD to feed the ATEM
4- Try a different ATEM box
5- Match the camera signal (frame rate, etc.) exactly to that of the ATEM (so no scaler or conversion is needed by the ATEM).

EDIT: I found another thread about that same issue here on this forum: viewtopic.php?f=4&t=113934#p627750