A further update on this. I'm leaving the hive going as I have others doing well and I am curious to see if this hive sorts itself out. I'm raising a couple of queens from a different colony in Nucs in case I need to requeen.
Anyway, today I had a quick look through and they are about 6 frames of brood, including about four sides of eggs. There was a fair bit of sealed worker brood but not much larvae, also hardly any drone brood. I did notice once cell with about four eggs and another with two, hundreds more had a single egg (checked with magnifying glass). I also took a good look at the queen, she was moving about fine, had all her legs and her wings looked fine.
It just seems she lays well for a while and then stops. Plenty of room with a few fully drawn and previously used frames.
I had hoped the colony would supersede but they don't seem inclined to.