Gap between infill and inner wall

I have some problems as shown in pics. Gap between infill and inner wall. I used zultrat material with z-ultrat profile. In different prints but the problem is the same. Which is the problem? The printer? The software? The material? If i will not resolve this I will resend back the printer. I migratet from a Pruso I3 hoping to have more time to project than setting, but this seems to be a problem for other owner of this machine. Hope someone can help me.!

Hi. Can you share the .zcodex and .stl of the model, please?