Bad quality in inner wall surface

[CormaplastEJCD 0]

I have the issue where I'm printing a coffee mug. Outer wall seems to have a reasonably good surface and is respecting the Z seams position. But inner wall surface has bad quality and shows some small gaps. I have set up the same slower speed for outer and inner walls in Cura. I'm printing in PETG with the suggested temperature, speeds, retraction settings, etc. How can I make Cura print the inner wall in the same quality of outer wall. 

[Smithy 710]

Please save the project in Cura and upload it here, otherwise it is hard to give some adivces.