How does overworld item spawns work in hideaways?

Question

I was curious if the items in the grand underground hideaways are random and spawn at regular intervals or if they're just set and don't respawn.

Comments

I have a friend who told me about items he found in particular areas, and I went and found them in the same places. So at least some element of it is set in place (prime example: Lucky Egg in the top-leftmost hideaway).

---

I dont have a source so I wont answer but the items are static. You always get the same item in the same place.