Okay the change to the power supply didn't fix the "cold boot" problem.

I futzed with it a bit and I was able to repro the problem on the test bench after chilling the assembly. And the thing that fixed it was...

Futzing with the I2S pins. (Specifically, gently touching the I2S pins with my finger.)

So I think that the I2S voltage dividers is the culprit. Removing those.

You're sure the empeg I2S runs at 3.3v and you're sure I won't fry another chip by running these things without a voltage divider?

Gonna try it... Crossing fingers....