Sequoia - Thunderbolt Dock Issues

I'm experiencing a serious connectivity issue since upgrading to macOS Sequoia 15.5 on my 2019 16" MacBook Pro (2.4GHz 8-Core Intel Core i9). Previously, everything worked flawlessly on Ventura, Sonoma, and earlier macOS versions.


Here’s my setup:


  • MacBook Pro 2019 16" (Intel Core i9) 64GB RAM.
  • OWC Thunderbolt 3 Dock


Connected devices:


  • Universal Audio Apollo Twin X Quad (Thunderbolt 3)
  • Neural DSP Quad Cortex (USB Type-B)
  • M-Audio Code 49 MIDI Keyboard (USB Type-B)
  • Samsung ViewFinity S65VC WQHD Monitor (HDMI)
  • WD Passport external HDD (USB-A)


Since updating to Sequoia 15.5, my MacBook rapidly switches between battery and power source every few seconds, chiming each time. This causes frequent disconnections of all connected peripherals through the dock. Sometimes the power delivery fails completely, or devices vanish and reappear.


Troubleshooting I’ve done:


  • Tested the OWC dock and all devices on another Mac running Ventura – everything works perfectly.
  • Performed SMC and NVRAM resets
  • Tried different power adapters/cables
  • Booted the Mac with the dock powered and unpowered
  • Changed USB ports and Thunderbolt ports
  • Updated firmware on connected devices where possible


None of this resolved the issue. It appears to be a compatibility or power delivery issue with macOS Sequoia and Thunderbolt docking stations, possibly specific to Intel Macs.


Note. Apple recommended I book a Genius Bar appointment, but my device is out of warranty, and I’m reluctant to pay for an assessment when this seems to be a software-related compatibility issue introduced by the macOS update - especially since the same hardware works perfectly on earlier macOS versions (and other Apple devices on previous OS).


Has anyone else experienced similar problems since updating to Sequoia?

Any suggestions or fixes would be greatly appreciated.

MacBook Pro 16″

Posted on Jul 19, 2025 2:52 AM

Reply
4 replies

Sep 5, 2025 4:42 AM in response to _kglenn

I am in the middle of collecting data from my own situations at the moment, but what I can tell you is this issue is not limited to old, new, intel, M4 ...

In fact it covers everything connected to any of the main port buses (or something of that nature). I first started digging into this because it's been many months now of having no mouse function to speak of. Whether USB 2.4ghz dongle or bluetooth magic mouse (2 different generations of those); all of them are jumpy and jittery or like they have a hot piece of gum under them making them impossible to use. I am a track and mouse guy for most applications, and I really didn't notice how much I use them both for specific bits until this all happened.

I have been chasing so many of these posts all over the internet from forum to forum, looking for solutions that last more than 5-10 mins, which is about the time everything works before sliding back to unusable. Instead what I found was that there was this guy who had my mouse problem AND (he thought unrelated) his power supply crapping out every now and then and taking all 4 USB C ports down with it. His machine wouldn't even acknowledge the ports until it dropped to 1% and then suddenly was taking power and seeing the ports again. I asked if he had had any issues with external drives at all lately? He said only minor things but his power supply? It's costing him effective work time and massive stress! But by then I'd gone back to all the places I found 15-30 messages all from people with problems with one thing in common ... their power management is buggered. I mean, they are saying it's just my external sound device, or my controller, or MIDI device, or ext ssd, USB HUB, or external monitor through the USBC display port, or bluetooth mice, or power supply, or network adapter.

So when they were advertising how proud they were of this new battery/power management system, as well as the adoption of more Thunderbolt and USB4 and ... now the voltage on my ports is all over the place as I'm watching the dongle I put inline to my power cord. So I move the ethernet to the other Thunderbolt bus. power settles to a steady charge draw within 0.1 watts. Solid. So I go look at my System Info ...

under Thunderbolt it says I have 2 USB4 ports per bus; 2 buses. Except that USB4 and was released for use August 29th 2019, and the Thunderbolt 4 specs were given to the USBIF to include in the new spec. "1 port to rule them all!" The first USB4/Thunderbolt 3/4 devices and cables started hitting the shelves late 2020 ... yes. weird. I thought so too. I bought my machine direct in december 2019, and it was made just slightly before Summer in China earlier that year. Not even a vague chance that I have those ports in my machine, and if it's trying to act like it does, then that may be the problem? Either way, there are at least a dozen issues that eminate from the same port buses and device connectivity. All of them could definitely be acting this way from dsregulated voltage. Yet not a word from Apple yet? I am going to submit what I have with my wild and crazy theory and see what they come back with. Who is betting "condescending dismissal", and who has endless run arounds and blame for my out of service mbp or nonstandard configuration? 🤓

Check out your voltage outputs for various devices. I'd love to hear what happens when we are directly testing for these things.

I know this is far from helpful but maybe when I drop the data in front of them they'll, want to help finally, or at least admit that their mistake is actually cooking peoples devices ;)

Aug 15, 2025 12:11 AM in response to _kglenn

This doesn't seem to be intel-specific. I'm having the exact same issue with a 2021 14-inch MacBook Pro with the M1 Pro chip.


At the moment of writing I can't get any work done, because my screens keep going off and on about once a minute. I've had to disconnect all my external storage from the dock for fear of corrupting them due to the sudden disconnects.

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Sequoia - Thunderbolt Dock Issues

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