Mac Studio M2 Ultra won't display 8th monitor

I have a Mac Studio M2 Ultra, which is supposed to support 8 displays. I can get 7 working, but not the 8th one.

My setup:

Front Thunderbolt Port 1: LG Ultrafine connected via TB with a simple FHD Sansui display daisy chained.

Front Thunberbold Port 2: N/A (this is where I'm trying to connect the 8th display, but the display says it is getting no signal.

Rear Thunderbolt Port 1: LG Ultrafine with Sansui FHD display daisy chained.

Rear Thunderbold Port2: LG Ultrafine with Sansui FHD display daisy chained.

HDMI: the 7th display, a Sansui FHD display, is connected to HDMI.

The info from Apple is that the Mac Studio M2 Ultra supports up to 8 displays with the following configuration:

a) Four displays connected to TB ports in the rear (which I have with the two sets of daisy chained displays),

b) Two displays connected via front TB port with daisy chain (which I have),

c) One display connected to HDMI (which I have),

d) One display connected to the other front TB port (which I have, but this one is not getting a signal apparently).

It's not the display; if I connect the USB-C cable coming out of one of the LG Ultrafine displays, this display works fine.

I've tried using a TB cable (same exact cable used for the other three LG Ultrafine displays) to no avail. I also tried a USB-C cable, also to no avail.

I do notice that if the mac is on and 7 displays are up, they do seem to flicker once briefly like they are resyncing if I then plug in the 8th display to the second front TB port.

I've plugged/unplugged/replugged the display multiple times from both ends of the cable. I've shut down and rebooted the mac at least twice. I've tried "detect displays" in the settings app. Nothing is working.

The Apple documentation pretty clearly says that this should work. Any ideas, or is the official documentation just wrong?