It would seem to be a SW problem for sure. I have followed the solutions in the thread you quoted religously several times, and also reduced to essential parts as suggested by Sineos. I suspect the limited resources of the old board may be the reason the patches fail. At some point, as intriguing as a mystery this is, it is time to move on.
I am fortunate that it is a hobby and I have the Frankenvinci working well. A new Pi is coming and I am working out a new purpose for the old Pi. I appreciate the efforts of everyone to solve this.