I think somebody here complained before about build in caps that does
not work.
Never used resonators with that build in myself. Try use resonators with
external 15pF caps.
Or swap the resonator with one from the working boards.

How far away is your resonator from the OSC. pins? Best to have it as
close as possible with direct tracks to the pins.

Normally when I get intermitted startups it, mostly it's noisy supply
lines. put some cap filters in. And since 90% of the time my PICS is
used in the industrial field, I always use external Power On Reset.
Sometimes as long as a one second delay.

Also, are your selection of oscillator type correct in the Config
register?

Hope this helps
Quentin