Regarding the PiccoloSD64 issue,
With your observations of reduced memory size and reduced bus speed, it's likely that you will fix it all by replacing that single Micron chip.
You were correct.
I managed to source 4 compatible NEC chips from a polish industrial components dealer, but swapped only the Micron chip out. After having done a long term test, I am sure this particular problem is now solved.
Thankyou for your assistance.
Regarding the PIV issue, I will test again as soon as OS3.2 arrives, and when time permits. Eventual findings will be opened in a new thread.