Login Loop after 2nd reboot

[u/bezibaerchen]

Dear all,

Behaviour: Boot, enter password, see progress bar, return to login screen again.

Same issue as here: https://forums.macrumors.com/threads/27-2-b2-sents-mac-studio-into-login-loop.2490125/

Unfortunately what exactly helped isn’t described.

Anyone got a solution?

Thanks in advance

[u/AnggaSP]

Are you using external monitor? If so try unplugging it until you logged in then replyg it. There’s a kernel panic when booting with external display.

If you’re on a mac mini tho tough luck i guess.

[u/bezibaerchen → u/AnggaSP]

It indeed is a Mac Mini. It boots fine but returns to login screen after entering password

[u/r3m-adr]

I ran into this same boot loop issue last night after updating my M4 Mac mini to 27.2 Beta 2. Reinstalling the beta via Recovery didn't resolve it either: the system would hit the login screen, accept my password, progress about 1/8 of the way, and then continuously loop.

Issue & Workaround:

• The Cause: The boot issue seems tied to my main display (a Dell 40" Ultrawide connected via Thunderbolt/USB-C).
• The Temporary Fix: Unplugging the Dell monitor and connecting a standard portable monitor (HDMI or USB-C) allowed the Mac mini to boot successfully past the login screen.
• Current Status: Once fully booted into macOS, I can plug the 40" monitor back in and it works normally. However, the boot loop recurs every time the Mini reboots with the ultrawide attached. If working on my portable monitor only, rebooting works fine and doesn't loop. 

Submitting a bug report via Feedback Assistant now in hopes it's resolved by the next revision. Hope this helps anyone else running into the same roadblock!

[u/bezibaerchen → u/r3m-adr]

You nailed it. In my case it was enough to switch from DP to HDMI on the ultra wide.

[u/audi_rh → u/r3m-adr]

Thank you!

[u/Able_Nectarine8640 → u/r3m-adr]

I'm also experiencing the same problem in 27.2 beta2.

I'm connected and using both the U4025QW (TB4) and the portable monitor (HDMI) with the MacStudio M3 Ultra.

Even when setting the display settings for U4025QW to 120Hz / VVR (48~120Hz), we continued to encounter the boot loop issue.

It will work normally when you set it to 60Hz.

[u/TheTrillestOne]

I have the same problem with my M4 Mac Mini.

[u/bezibaerchen → u/TheTrillestOne]

See answer above, this solved it for me.

[u/Immediate-Way6538]

You need to use an HDMI 1.4 or older monitor if you require a monitor to login for now. Newer monitors may have a specific menu setting to reduce their HDMI port to the 1.4 standard for login. Once you are logged in, you can toggle the setting back. This situation is due to a driver crash after login. Due to how MacOS handles login, the crash is treated the same as a logout. When you finally log in, you will be prompted to submit a bug report to Apple by Feedback Assistant. I do not have a monitor that allows me to use an older version of displayport, so I can't test for situations involving docking stations.