I am by NO MEANS an expert. But here is what I know happened in my house:
Frist, Jenni, my cage looks extremely similar to yours. Purple high-side plastic bottom with about 3/8" gap white wire caging. It ios the SAME cage my roomate used when he got his first rat. So here's the story---
My roomate came home with a smallish grey rat and this cage. After about 3 weeks, we heard a lot of LOUD squealing coming from his room, went in there and the rat was nowhere to be seen. When we lifted the hide, she was laying there in almost convulsive conditions, shaking and shivering. The entire length of her tail was de-gloved, and broken in SEVERAL places. We could not find the skin anywhere. We don't know how it happened, but can only assume that while she was climbing on the cage walls(which she did frequently), she must have somehow gotten her tail pinched between two of the sections of wall in the corner, where the walls are able to be taken apart for transport. Getting hung up, she must have fought HARD to get untangled, stripped and broke her tail, and went to hide. Unfortunately, her tail became severely infected, and she needed to be put down.
Fast forward a couple months...I now have the cage as I am getting 2 rats for feeder-breeders. We both(my roommate and I) assume that the incident with HIS rat was a "fluke" and shouldn't be an issue because, as you found out, MOST reputable rat breeders recommend cages over aquariums. So I put my rats in this cage and they LOVE it...climbing all over the walls and just "playing" around, enjoying themselves. I've had my rats in there for about 3 weeks or so, and late last night I heard this VIOLENT squeaking and squealing. I go into the room...no rats. So I move the hide and my male is hovering over the female towards her tail, and the female is, again, in a convulsive state. Her tail is broken badly about an inch or so from the tip. It isn't de-gloved, but there is a small wound and an extremely awkward angle...OBVIOUSLY broken.
I don't know how, I don't know why. But I know that it has happened to TWO rats at TWO diffenrent times with the same cage...which is VERY similar in appearance to the one you show in your pictures. I am not taking anymore chances. They are now in a well-ventilated plastic case with cage top. I am certainly trying to let my little girl heal, as her injury is not even close to being as viscious as my roomate's rat. But for me and my money...I won;t use those cages anymore. It's too risky, IMHO...