Mine did exactly the same lolive tried one of these,it was used for about 20 mins,then they sat in it and wee,d and poo<d in it !i just use it for floor time once a week.the carrot cottage and hay tunnels ive had a much better success with !
You could always buy dried forage and sprinkle it over a nice hay and stick the lot into an underbed storage box. Same thing but no soil. Think I will try that myself.