I used to have two otherwise identical displays, but it still does it for me now that all of my displays are different. Notably, I think this stuff happens more when you have 3+ monitors. I don't remember having as many issues with just two displays.
Comments
It is typically because you have more than one of the same monitor with identical EDID information.
Documented and explained here: https://spin.atomicobject.com/2018/08/24/macbook-pro-externa...
Possible fix: https://gist.github.com/ejdyksen/8302862?permalink_comment_i...
I used to have two otherwise identical displays, but it still does it for me now that all of my displays are different. Notably, I think this stuff happens more when you have 3+ monitors. I don't remember having as many issues with just two displays.