So glad it worked out!  Was the key solution cutting the flour with cornstartch?

The thing about the butter pieces is that the larger they are, the flakier the crust.  Frozen butter does have a tendency to shatter, I wonder if refrigerated butter plus frozen flour might work?

Brought the protein content down to around 9 grams.

Refrigerated butter sounds worth trying but it flies in the face of pastry doctrine. I guess I am a rebel at heart!

I do have a powerful French food processor which might account for splintering.

I made pastry again today (Cream cheese) and paid particular attention to be on the lookout for the “phantom” pea sized particles.

I know you see these when you make pastry by hand - I am still not sure whether they are so visible using a food processor.
Most pastry recipes want one to stop pulsing just as the mixture starts to come together - before it becomes a ball.

Rose’s method of course ensures tenderness.

I would love to try the by hand method but its mid-summer here with temps of around 85F. Have to wait for winter when we have a cooler 65F!

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Just made an apple pie over the weekend, and noticed when I blind baked the crust that there was more shrinkage of the sides where my oven is cooler, and less where it has hot spots.  So just wanted to add that a relatively high oven temp can also help set the pastry before it shrinks.

I know Rose believes in high temps so the crust sets quickly.
Your baking supports this.

I think I am switching to convection baking soon. No more hot or cold spots!
I have been impressed by some tests. Very even baking.

Sounds great, I think most pastry does well with a good quality convection oven!