Thanks, and now some more progress
I bought a big bag of moss to turn Pearl's whole tub into a laybox, to see if it would help. While she was in a feeding tub, she started contracting and pushed an egg right up to her vent. I closed my hand around her and gently helped the egg out as she contracted. (I can't emphasise enough how nervous I was and how gentle the manipulation was)
So now I have 6 good eggs and Pearl is burrowing through the damp moss