I did! [1]
There was some initial activity, and we got it narrowed down to a range of commits, but did not get any real smoking gun.
To be fair, I also put in less effort once I found I could just copy the 11.3 loader and get things working. And also some stuff came up in my own life that prevented me from devoting more time to it, alas.
It eventually got auto-closed for not being tagged to any non-EOL versions. I did recently confirm it was still a problem on newer releases, but that hardware died not long after, so I didn't pursue it.
My best guess is that it was some BIOS-level oddity. It's also possible that it was due in some way to the hardware (slowly) dying; I can't be sure. But it was a very clear "worked on release X, stopped working on release Y (and beyond)" sort of behavior.
That's interesting/strange. Did you report it? I'd expect them to care about that serious of a breakage in a point release.