Hey Primoz It looks like problem with temperature. The base of your model is much larger, which allows the filament to cool down on each layer, but as your model starts to get thinner at the top, the material doesn't have the same amount of time to cool. Try printing two at a time, or place a cylinder next to your model that is a little higher and tell cura to print both at the same time.
this object is too tall and when you reach some height it begin to flex. Then you must print slowly and, for more stability, You can create a structure to make the object stronger.
I suggest you to use Meshmixer in which you can look where the piece is too weak.
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