looking at the video of the 'thorn' gun. It's in several parts.
So the part you are having problems with can be split from the rest, printed seperately and moved to a different part of the bed.

If that doesn't work, then you need better bed adhesion.
Settings look fine, 70c is a bit hot for pla - 50-65 is usually better.
If the bed is too hot with pla, then it will stay really soft, which could be one reason that part is lifting.
Magigoo and a cooler bed will fix that.

Try 55c for the bed and 150% thickness for the first layer.
Gettin a thicker firstlayer down acts like using araft and can fix this kind of issue.