It's not your fault
Hamsters do better with lower height and more floor area. If they climb they often just drop and can injure themselves. The problem with it really is the floor area is very small at 50cm by 36cm. It's generally considered that the old RSPCA minimum of 80cm by 50cm (or more) is a suitable size for a Syrian hamster.
The height of the cage at 47cm is quite tall. It is only 1 or 2 cm taller than the Barney cage - but the difference is the barney cage has a deep base to fill with substrate, which can effectively reduce some of that height. With a tall height and shallow base, it's not ideal.
The way the shelves are set up means there are a lot of gaps to fall through from the top and hit things on the way down. Hamsters can climb to the top and even monkey bar across the roof - and they tend to just drop - they aren't good climbers really. They are more ground-dwelling and diggers.
The house at the top isn't really good for normal behaviours. Normal behaviours are to bury food under their nest so a house on top of the substrate is better. Plus they tend to have a toilet area near the cage and it's a long way down to go for a pee! So they may just do it in the house instead.
It is annoying - I have been there myself, having bought a 3 tier rotostak thingy for our first hamster. And it was a wrench upgrading him to a better cage in some ways because the design of the rotostak was really quite clever, the little bottle holders etc. Unfortunately it was just totally unsuitable for a hamster to live in.
Their cage is their environment really and within that they need a nice darkplace to nest and retire to - then space to come out and forage and do things and mess about with piles of substrate (normal behaviours).
There is nothing wrong with having platforms - it's good to have a platform, but the set up needs to be safe and work for the hamster. It's not the worst cage but it's not a good one, even though it looks nice
I believe it is quite easy to escape from as well with hamster's having opened the doors quite easily - although that is solvable.
Sorry - I don't mean to be rude about your cage. Unfortunately pet shops just sell cages for profit and there is no real safety or suitability legislation. So we poor owners end up making expensive mistakes sometimes.
There are quite a few good cages - the Hamster Heaven, Barney, Alaska and Alexander on Zooplus and various other Savic and Ferplast cages. But an awful lot of unsuitable ones sold that are easier to find sometimes.