[cypher]

I didn't think you'd had her that long, cage size is much less likely to be an issue in that case.
It may just be the catching & cleaning routine as you thought.
Do give the other ideas a try though, if she uses the other box for her stash leave that well alone! Even when cage cleaning leave the stash or replace it with fresh.
I find my hams don't like things being changed much in the cage once I have a set up they like, maybe keep one small area where you might try swapping one or two things around.
If you don't have space for a coconut small terracotta flower pots are a great alternative, all of mine enjoy having a dig around in those & they're good for nails too which is a bonus!