Opencore 8.3.0 installer hangs before Big Sur Installation

Hi, I'm trying to install Big Sur to a 2015 Lenovo Thinkpad Yoga 12 and it's hanging during the output logging messages while booting up the opencore installer. There doesn't seem to be any kernel panic, it just stops printing messages and sits there forever.

SPECS:

Intel Core i7 5600U (Broadwell)

Intel HD 5500 integrated graphics.

8 GB RAM DDR3

1TB Samsung QOV SSD

Conexant CX227751 audio controller

Realtek RTL8153(?) ethernet (from Thinkpad Onelink Pro Gigabit Ethernet docking station)

Intel Dual Band Wireless-AC 7265

I'm following the opencore install guide from Dortania, specifically the version for installing Big Sur on Broadwell Intel laptops: https://dortania.github.io/OpenCore-Install-Guide/extras/big-sur/

I get to the part where I see the "picker" and select my EFI partition off the USB stick. Then I see some messages about loading the OpenCore.EFI file and it looks like it starts going into system initialization. This is where it hangs. The last part of the open core log looks like this:

101:659 00:049 AAPL: #[EB|RH:PF] usr\standalone\OS.dmg.root_hash 101:719 00:059 AAPL: #[EB|RH:MF] <"usr\\standalone\\OS.dmg.root_hash.x86legacyap.im4m"> 101:771 00:051 AAPL: #[EB.LD.LF|IN] 0 1 <"usr\\standalone\\OS.dmg.root_hash"> <"0"> 101:825 00:053 AAPL: #[EB.LD.OFS|OPEN!] Err(0xE) <"usr\\standalone\\OS.dmg.root_hash"> 101:874 00:049 AAPL: #[EB.RH.LRH|P!] Err(0xE) <- EB.LD.LF 101:924 00:049 AAPL: #[EB.BST.FBS|!] Err(0xE) <- EB.RH.LRH 101:976 00:051 OCSMC: SmcReadValue Key 4D535463 Size 1 102:027 00:051 OCSMC: SmcReadValue Key 4D534163 Size 2 102:077 00:049 AAPL: #[EB.B.WFDW|!WF] Err(0xE) 0 102:126 00:049 AAPL: #[EB|LOG:DT] 2022-09-06T00:33:44 102:178 00:051 AAPL: #[EB|LOG:EXITBS:START] 2022-09-06T00:33:44 102:860 00:682 AmiShimTimerBoostExit changed current period to 549254 

Pastebin link to full log: https://pastebin.com/TPSb1HY8

What displayed on the screen was different.

https://preview.redd.it/pnblv0e167m91.jpg?width=3840&format=pjpg&auto=webp&s=19833be4a763f4fe0e7ccf24a20e38aa519a88b3

And I believe the 4 lines that contain `Err(` on them might be a problem. Also note that it stops just after the EXITBS:START message too.

I looked through the opencore troubleshooting page in the guide for EXITBS:START: https://dortania.github.io/OpenCore-Install-Guide/troubleshooting/extended/opencore-issues.html#stuck-on-a-black-screen-before-picker

But all of these solutions I've double checked and seen that the config plist areas seem correct.

Pastebin link to my config.plist: https://pastebin.com/0Z7aiJM5

I also attached a small screenshot showing the kexts I included. As for SSDTs, I have SSDT-PLUG, SSDT-PNLF, and SSDT-EC (the one for laptops).

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https://preview.redd.it/j2lgezlv57m91.png?width=201&format=png&auto=webp&s=371010f0848cb837644b5784edff43f9c84de318

If I google the error lines, I can see previous people stuck on Big Sur installations in the past. However, they don't seem to have the same problems as me.

Here: https://www.tonymacx86.com/threads/big-sur-installer-error-in-opening-usr-standalone-os-dmg-root_hash.306845/

This person solved it by "starting from Vanilla"? Though I have no idea what that means... I'm also unable to run the suggested configurator because I don't have a working mac OS.

Another one here: https://github.com/SchmockLord/Hackintosh-Intel-i9-10900k-AsRock-Z490-Phantom-ITX-TB3/issues/12

These people ran into some bug with opencore 0.5.6 -> 0.6.3 where RebuildAppleMap and AppleXcpmCfgLock were swapped. I'm using 0.8.3 and the two values in my config.plist are the right way around.

The gist of the problem looks to be some sort of read error trying to get to `usr\\standalone\\OS.dmg.root_hash` for some reason. I recall one of the forum members saying that the filesize was expanded for Big Sur and this was kind of common to see. I'm not sure what that means either, but maybe it'll jog someone's memory?

I wonder if anyone might have some idea of what is happening here?

Thanks!