URSA Broadcast G2 gain flicker when plugged into program ret

Fairly standard set up - URSA Broadcast G2 running two SDI cables into bidirectional (I have tried two), then HDMI into the ATEM Extreme. It is causing a flashing effect on the camera, which looks like it flicking between its two base ISOs (this is reflected on the histogram.) When this is happening, the ATEM also isn't getting a video feed. It stops when the return cable is unplugged.

I have tried two bidirectionals, I have tried different cables, different power for the bidirectional, nothing seems to make a difference. I also tried shutting off the ATEM, and this behavior continues. Both camera and ATEM are set to 25fps, (the camera is sending 1080p.) Also no visual sending bars from the camera (but this works fine with the return cable unplugged.)

Any suggestions?

Edit: Just plugged in my old 4.6K and it's working fine... I am going to try resetting the broadcast.

Edit 2: Exact same behavior after reset. (Yes, I did make sure to set it back to 1080 after the reset.)

[Gary Adams]

Without feeding something on the HDMI input on the Bidirectional the URSA will get its own output fed back to the input. This camera reacts differently than som of the other models. Make sure the camera reference is set to Internal. It would be best to feed something to the HDMI input of the same frame rate like the program of the ATEM Mini to prevent this from happening. I hope this helps.

Gary