HDMI feed from MAC Studio M1 keeps dropping

We have a MAC Studio M1 configured with four display outputs, three connected through USB-C HDMI dongles. The computer runs ProPresenter 7. PP7 is configured to display the desktop on one monitor, Audience on another, confidence monitor on another and the stream feed to an ATEM mini on another. The desktop is fed from the HDMI on the PC; all others from the dongles. All dongles are Apple USB-C. Occassionally and without any warning, the stream feed will drop off, going blank. The MAC display settings show no indication of disconnection, and neither does ProPresenter. When I unplug the HDMI cable feeding the ATEM from the dongle, the ProPresenter desktop display also drops off, going back to the computer's main desktop display. When I reconnect the HDMI, both the ATEM stream feed and the ProPresenter restore. Then, again, a few moments later, the stream feed will drop off again, going blank. I don't understand how this can happen. Any advice on how to proceed will be greatly appreciated.