Similar experience, but in reverse. Have 4K Dell S2721Q that exhibits your on/off behavior. I swapped the power cable between it and my 2721DGF and it alleviated the problem. Used to be practically constant on/offs, now only does this occasionally after waking display. Power cycling then fixes. Not a great experience or solution, but try some diff power cables (C13) if you have some around.
https://www.indexxx.com/m/jade-maris
Similar experience, but in reverse. Have 4K Dell S2721Q that exhibits your on/off behavior. I swapped the power cable between it and my 2721DGF and it alleviated the problem. Used to be practically constant on/offs, now only does this occasionally after waking display. Power cycling then fixes. Not a great experience or solution, but try some diff power cables (C13) if you have some around.