Whenever weird stuff happens I suspect alkaline damage. It's easy to look for, usually easy to find, and sometimes hard to remediate.

Post pictures of your boards. Well focused, high resolution. Especially near the batteries or where the batteries used to be if they have been relocated.

I'd try a factory reset as described in the manual in section 3, chapter 6, page 51 on the bottom of the page.

What is this blob near U405?
LotRpcb01arrowadded (resized).jpg

Edit: If you need someone to playtest in the name of science let me know. I'm just up the road.

Here is the readme from v10, currently available from Stern's website:

"CPU Release 10.00
Date October 28, 2005

Game ROM 1M U210 $84FF 10.00 lotrcpua.A00
Game ROM 1M U210 $9DFF 10.00 lotrcpul.A00

- *** THIS CPU RELEASE REQUIRES DISPLAY VERSION 10.xx ***
- *** IMPORTANT INFORMATION ***
If your game shipped with version 9 software, then please read service
bulletin #157: http://www.sternpinball.com/SB/ServiceBulletin_157.html
If your game is affected, please update your sound OS before installing
this code update, or the problems will get worse.
- Fixed a bug with entering initials for Destroy the Ring Champion when it
was earned during a ToPS Tournament game.
- Cleaned up some hacks related to Sound OS problems (the 9.0x releases, not
in 9.00).
- Fixed a bug where Palantir might try to add-a-ball when all balls were
already on the playfield during multiball.
- Fixed a bug where the game would show the FOTR MB Lit display effect AFTER
you had already started it (this happened if Pippen was the last person to
be collected).
- Russian (& other country) coinage/tournament settings added."

Service Bulletin 157 is located at https://sternpinball.com/wp-content/uploads/2018/10/sb157.pdf
It reads in part: "T3 (tm) was the first game to start using the new White Star CPU/Sound II Board (SPI Part Number: 520-5300-00). ThisPC board utilizes new hardware in the sound section. This hardware required a newOperating System (O/S) in softwarethat has been continually improved and updated since T3. This has created some compatibility issues between thedifferent versions of Operating Systems. One example would be games using sound ROM’s programmed to work withO/S 5 will not work correctly in a board programmed with O/S 4. The version of the O/S can be identified by the numberof times LED1 flashes upon power-up (e.g. TheLED1 will f l i c k e r then flash 4 times = O/S 4, ... 5 times = O/S 5,etc.). Note:Color dots**are used on the IC in position U8 to also determine O/S Version for boards."

My next step would be different ribbon cables. I wouldn't buy new ones unless a different set fixed the issue. Get on the Bat City Pinball facebook page and ask around, or maybe Brandon Haney with Oldies But Goodies pinball has some you can try.

Maniac, what do you think audit 227 refers to? Nothing in the manual that high, and it's various numbers in the video.

Revisiting this, Red_Devils is still having the same problem.

Anyone know what section of the Whitestar board generates those errors? Something in the boot process looks for those errors and it’s either getting bad data or outputting bad data.

Maybe booting with the playfield disconnected would help isolate the problem?