Issues with Thunderbolt connection/display since updating to Sequoia 15.7.3.

Looking for help as I was unable to get a resolution with Apple Support. I have recently encountered some issues with Sequoia 15.7.3 that had not previously existed. System Mac mini purchased in October of 2025 connected to two Dell U2527QE monitors (Both on latest firmware), Monitor (1) is on the left and horizontal, Monitor (2) is on the right and vertical. These monitors work as hubs/KVMs all peripherals are connected via the monitors, Monitors have the following connections:

• Monitor (1)
  • Thunderbolt in from Mac mini,
  • Thunderbolt out to Monitor (2),
  • 3 USB devices plugged in (dongle for Mouse/Keyboard), Webcam, External HDD)
  • USB-C out to Surface Dock
• Monitor (2)
  • Thunderbolt in from Monitor (1)
  • 2 USB devices (Light, External HDD)
  • USB-C to 3.5mm Audio connector
  • Ethernet Cable

Prior to Sequoia 15.7.3 both monitors showed a 120 hz. refresh rate, login appeared on monitor (1) when restarting/powering up, Ethernet connected automatically, and display settings where retained.

Post update to 15.7.3 I am having the following issues:

1. Login occurs now on Monitor (2)
2. System is inconsistent on if it will retain display configuration (often reverting to seeing both in monitors as being horizontal and switching order3)
3. Refresh rate on the second monitor is capped at 60hz, but this will vary (meaning sometimes monitor 1 is capped, other times monitor 2 is capped.
4. Ethernet connection is no longer detected.
5. When hovering over the Green Resizing window It shows the option to move to the other monitor, however When the window is on Monitor (1) it indicates that I can move to Monitor (1) but then moves it to Monitor (2), same but reverse happens with windows open on Monitor (2). If I rearrange the monitors so that Monitor (2) is the left then then the numbers work properly (however this is not a real solution and just makes navigating on the screens overly complicated). System seems to be hard set that Monitor (1) is on the Right, and Monitor (2) is on the left despite how I arrange them and what reality is.

If I unplug/re-plug any of the Thunderbolt cables I can get Ethernet to be recognized, however display configuration may not be retained. I can keep unplugging/re-plugging the thunderbolt cable get everything but the refresh rate and resize button back to normal but all this goes away if the system restarts.

If I plug both Thunderbolt cables directly into the Mac Mini then all issues appear to resolve, but this is not an acceptable solution as the connections are shared between two systems.

Steps done to resolve: I have reinstalled the OS (under direction of support), updated firmware on Monitors, done various other trouble shooting steps leading them to saying it would need to get escalated to engineering. Support will not escalate to engineering team unless I update to 26, this is not an acceptable solution as I find liquid glass to be problematic.

And yes, I recognize these are trivial problems in the grand scheme of things, but I am just looking to regain the functionality/user experience I had prior to this update.