If it’s difficulty walking in the unevenness, what I did with our last Robo (who was ageing abd had mobility issues due to a lump) was use hemp mat on top of the substrate. So it was still the same height but a level surface all over the cage. It worked very well. I cut holes out for round the sand bath so it could be sunk into the substrate with the top level with the hemp mat and left one little corner free with substrate showing in case he wanted to dig but he didn’t bother. He speeded up round the cage no end.
The photos are on this page
Nugget's thread