Personally I would also give it a little more time for him to settle in. Although I can understand it can be worrying if he's doing this, but he's unlikely to hurt himself as you have lots of lovely thick substrate in there for him to land on and it's not that far to fall from the roof to the top of his house.
It sounds like he might be feeling a bit stressed, temporarily and wanting to see if he can get out - which they sometimes do when they feel a bit stressed - sometimes with changes to the cage, but they can be distracted out of it. A bit of out of cage time and some scatter feeding maybe.
I am just wondering also if he can still smell the scent of a previous hamster although I'm sure you c;leaned the cage out between them. But sometimes it can linger on the bar area. I had a situation like that once, where the hamster and cage had been left at a pet sitters where there were other hamsters and he was very stressed on his return for about two weeks - it's not nice to see., In the end it occurred to me his cage may smell of the other place or other hamsters so I cleaned the cage including wiping the bars down inside and out - either soapy water or a half and half white vinegar and water. Normally it's best to avoid a full cage clean as that can cause stress in itself - but on this occasion it did the trick, because it removed a scent that wasn't the hamster's scent. It helps to save the nest and replace it though, as that has their own scent. Has he built a nest yet? It needs a big pile of toilet paper strips in the cage, then they can build a nest. He has a lovely house in there to build a cosy nest.
There are a few other things you could try first - putting some treats in his house to tempt him in there, and scattering a bit of his food in the cage at feeding time (as well as in his bowl). He's still only a baby really and they can be very active and curious and see if they can escape sometimes. Do you have a playpen or "fenced off" area of a room he can have some out of cage time and taming with you?
Is he actually chewing the bars as well? That noise can drive people crazy! And it's not good for their teeth. You can weave cardboard round the bars in the area he's doing it if that's the case. That can distract them and give them something else to chew!
It could be a combination of a few things but he is maybe a bit stressed by something. It can be better to make any changes to the cage while they're out of the cage in a secure place (like a pet carrier) and get it all sorted and then pop them back and let them settle in again for a few days.
Our current Syrian is very active and he climbed the bars a bit at first but he soon settled down and stopped doing it. Food is always a distraction! Does he have a chew stick? They love the mini whimzee dog chews. The toothbrush ones you can stick sunflower seeds in the bristles.
I can understand if you want to make a bin cage, if it doesn't settle down - but it would need to be at least as big, or bigger than the current cage or he could still have stress. It also still needs a platform in really.
Hope things are settling down!
I’m going to have to do something/upgrade his enclosure.
