Mouse stuttering when an external monitor is connected

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Level 1

9 points

Mouse stuttering when an external monitor is connected

I get mouse stuttering/lag (a stutter every 2 seconds or so) when I connect an external monitor (iiyama 27" 4K) to my MacBook Pro (16", 2019) running Catalina 10.15.7.

This happens with every kind of mouse/trackpad. It happens when the monitor is connected with an USB-C to DP cable, and it happens if the monitor is connected to my CalDigit TS3+ with a DP-DP cable.

It seems I am not alone and these threads seem to describe the same symptoms:

https://discussions.apple.com/thread/251025198

https://discussions.apple.com/thread/251656464

MacBook Pro 15″, macOS 10.14

Posted on Nov 21, 2020 9:28 AM

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Answer 1

jwr777 Author

Level 1

9 points

Nov 30, 2020 12:21 AM in response to MichaelB2019

These questions are beside the point. I "solved" the problem by swapping monitors. The stuttering issue was present with the Iiyama PL2792UH (XUB2792UHSU-B1). It does not happen with a Dell P2715Q.

It also does not happen on a 13" MBP with integrated graphics. So, everything points to a problem with the Radeon discrete GPU in the MBP 16".

I replaced the iiyama with the dell and can now enjoy a working system, but the issue is still there, and as other posts indicate, I am not the only one suffering from this. I'm posting this hoping that it will get indexed and will help others avoid jumping through hoops (like setting up new user accounts).

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Answer 2

Nov 29, 2020 1:29 PM in response to jwr777

Hi jwr777,

Thanks for coming to Apple Support Communities for help today with mouse lag and an external monitor.

In one of the threads you posted, this issue wasn't present when the Mac was booted into safe mode. Did you try this? What did your find? Start up your Mac in safe mode.

What happens if you create a new user account and test the mouse there? Set up users, guests, and groups on Mac.

Let us know.

Have a fantastic day!

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Mouse stuttering when an external monitor is connected

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