External 4K support through USB-C stops working (after Sequoia 15.4.1 update)

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External 4K support through USB-C stops working (after Sequoia 15.4.1 update)

MBP M4 MAX connected to external displays, a 4K BenQ Monitor and an old Thunderbolt Display. All connected through a OWC TB dock. This setup worked fine since months. Then I upgrade to Sequoia 15.4.1 from previous Sequoia version and now it seems I am not able to connect the external monitor with a 4K resolution. Only the 2Ks are shown.

Nevertheless connecting with HDMI either directly to the HDMI connector or to dock using an HDMI to USB-c connector (dock has no HDMI connector) then back to normal.

Is there now a deprecation of some protocols (DP,HDMI whatever) over USB-c announced?

Posted on Apr 29, 2025 3:09 AM

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Answer 1

M0ll3art Author

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Apr 30, 2025 3:57 AM in response to Servant of Cats

one external monitor is a BenQ 4K, and when connecting this monitor now, only 2K resolution is offered. It is connected with a USB-c cable to a TB Hub. The 2nd monitor is an old Apple thunderbolt display (mini2TB adapter) also connected to Hub. The 2nd monitor shows the normal resolutions, as it was before.

what is new, is that I did not change the setup, and the BenQ which was running at 4K before, suddenly, can only be operated at 2K with usb-c cable. Observed after the Sequoia 15.4.1 update.

Now, if using an HDMI and hdmi2usbc adapter plugged into the TB Hub then it works at 4K as it was before.

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Answer 2

Apr 29, 2025 12:03 PM in response to M0ll3art

You refer to "2Ks" (plural).

To clarify: How many Thunderbolt Displays are we talking about? One? Two?

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Answer 3

M0ll3art Author

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May 1, 2025 11:45 PM in response to Servant of Cats

it seems that I perhaps mistakenly replied to my own post instead of yours. Sorry new to this community as poster..

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