[jakear]

This just started happening to me on Mojave, after I messed around with installing some third party USB managers to try to get my new keyboard and mouse to behave. Deleted the managers and returned the hardware, but some lingering issue crippled my multi-monitor setup. It’s particularly bad because I use one horizontal one vertical.

[BlackFingolfin]

While I don’t have that particular issue, I have other issues related to external screens, with 10.14 and 2018 MBP: I usually run the laptop with closed lid and an external screen at work and at home; and use it in “laptop mode” during my commute. Now, sometimes (once a week?) when I plug it into the external screen, it just won’t wake up, unless I open the lid, and then it still won’t recognize the external screen. Have not yet found out a reliable way to resolve this, but I usually manage with turning the monitor off and on again and/or unplugging/replugging it, possibly a couple times each.

Much worse is that sometimes (once a month?) during this process macOS completely messed up all my open windows: they are all resized to a tiny size. And I have dozens or hundred of them open. This is horribly annoying, and didn’t happen to me before (in 10.11; I skipped 10.12 and 10.13, for reasons similar to the OP. Before that, I went from 10.8 to 10.11; before that, I never missed a release, often was running beta of the OS etc.; but starting with 10.9, too many issues made this undesirable).

I dread switching to 10.15; unfortunately, I will get a new MBP 16” from work, which normally I’d relish, except that there seems to be no way to use it with anything but 10.15. I’ll see if I can delay it until 10.16 is out and will pray that they started to prioritize bug fixes again, but I have little hope that’ll actually happen.

[TacticalTable]

> I have other issues related to external screens, with 10.14 and 2018 MBP: I usually run the laptop with closed lid and an external screen at work and at home; and use it in “laptop mode” during my commute. Now, sometimes (once a week?) when I plug it into the external screen, it just won’t wake up, unless I open the lid, and then it still won’t recognize the external screen. Have not yet found out a reliable way to resolve this, but I usually manage with turning the monitor off and on again and/or unplugging/replugging it, possibly a couple times each.

I've previously had these problems, and they were made dramatically worse on Catalina. Each monitor has about 50% chance of correctly loading in, on what used to be 90%. My USB mouse (which is plugged in to the displayport monitor) also loads the incorrect drivers until I unplug and replug it.

[jen20]

Ah, I’ve never tried in clamshell mode - long harboured fear of the thermal envelope from the PowerBook days.