Catalina sudden dual monitor issues

[tombaugh]

I'm using my MacBook Pro 2018 in clamshell mode with two monitors, the primary being a 4K LG 27UK850 over USB C, and the second a 1080p HP Pavilion 22xi over HDMI and USB C. This has worked without issues for months. When plugging in my MacBook today, I found that the primary and secondary monitor had switched, and my mouse appeared to lag significantly. I have now switched the monitors back in the display settings, but my mouse is still very laggy and slow (even in the fastest tracking setting). Disconnecting the secondary monitor solves the issue, but as soon as I reconnect it the lag is back. I'm on macOS 10.15.3.

I'm not sure if this is relevant, but at home I'm using the MacBook in clamshell mode with a single 27UK850 monitor.

 

[tombaugh]

It seems that the 4K display was only getting 30Hz. Fixed by switching the 4K display from "Scaled" to "Default for display" and back to "Scaled". Somehow now it's getting 60Hz.

 

[tommiy]

Yep...just Catalina and external monitors. Similar behavior with my 2 external monitors...and another 4 other reported issues......

 

[roliwage]

I can't believe this is still a problem. I have an iMac from 2017, and after updating to Catlina (worst mistake of my iLife) it will either not recognize my external Cinema Display 23 at all, or will some how discover it about 30-40 mins later (the main display will glitch a little, then the 2nd monitor comes on.

I've been in touch with Apple Support and they only offer the same non-working solutions (PRAM, repairing permissions), and claim they haven't heard of this problem yet. That is such BS because their forums are full of people with the same problems. Catalina is a disaster.

 

[tommiy]

Yes been going on for myself since 10.14.6. The last known working version that I had no external monitor issues with was 10.14.5 released May 2019. A long time between releases that work and function. I don't expect it to be fixed in the next year to tell you the truth. I've simply ceased updating at all because I do not want to inherit additional issues or problems which appear in each minor release.

 

[Erlang]

I had problems with external monitors and Catalina develop, iMac (Retina 5K, 27-inch, 2019 ) with two external monitors, one began dropping out until this AM it never came on.
Display connected by TB3 to Caldigit dock with 2x DP.

Plug/ unplug, switched affected monitor to alt cable, NVRAM reset nothing worked. Switched to DP from another TB3 device, nothing.

Checked monitor by plugging in HDMI source, monitor fine, still no DP from iMac. Tried Detect monitors in Display Pref, could not see the missing monitor.

Power cycled Caldigit, and iMac.

on rebooting ColorSync Utility launched, for no apparent reason.

set external monitor profiles for sRGB, and both external monitors work fine now.

Not sure what fixed it. But looks to be software driven.

 

[tommiy]

There are alot of external monitor issues with Catalina. This includes Caldigit. you seem to be a lucky one where its started working. Refer to the 18 pages here on Apple Community. Seems firmware is breaking things. I suppose the question is is the firmware on the MAC actually correct?Its difficult to tell now as Apple stopped publishing the info of what correct is. Howver I remember some article last December where out of approximately 50 iMACs surveyed about 50% had the incorrect firmware. Apparently the upgrader in the OS upgrades does not stop the upgrade of the OS if the firmware install fails. There are apparently tools to check. Think from memory it was "silent night" but again its against some one pulling apart the upgrade to determine what is correct. You can check maybe its incorrect firmware.

There is also this thread specifically relating to HDR issues with 10.15.4 on LG Monitors that you may strike as well. Only 4 pages of feedback n this one.

 

[sinectica]

Hi,
I had similar issues with my macmini late 2014, Catalina 10.15.5 and HP PAVILION 22xi monitor, connected with HDMI cable. After restarting the computer, the resolution was not configured/detected and I always had to change it into the correct one (1080p)
I've been crazy resetting the NVRAM, PRAm, SMC... and nothing
What I did finally: I disconnected the HDMI cable and connected mini DVI adapter to VGA with VGA cable to the display. After restarting the computer with this cable, the system recognizes the HP monitor OK.
Of course it's not a solution, but by the moment I can survive with this config...

 

[adermard]

I have been having a similar issue with my 2018 Mac mini running Catalina 10.15.5. I have a TB3 monitor and and HDMI monitor connected. Occasionally when it wakes up from sleep it can no longer detect the HDMI monitor, it is black and it is not visible in System Preferences > displays. The HDMI monitor just drops out and no amount of plugging and unplugging the wire will help. Restarting the computer works and the monitor works fine until it sleeps again and then it drops off.

This post help me find the issue. The Color Sync Utility showed that there were three profiles for the monitor that kept dropping out. I disconnected the monitor. Deleted all of the profiles from the path where ColorSyncUtility shows they live. Reconnect the HDMI cord and the monitor is discovered and working properly. Now there are only two profiles for that monitor and it comes back from sleep correctly.