Print quality worsens after the first few layers

[weaselbandit]

Hi all

I have a Wanhao I3 Mini and I've started to have this problem on pretty much all of my prints.
The first few layers are perfect.

Perfect connection to the bed, no space between walls and infill and then gradually it looks as though the nozzle comes too close to the print.
The wheel that pushes the filament starts to click and the higher the print, the worse the quality.
What could cause this?

Thanks.

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