Cura making prints bigger

[Nannyogg82 0]

So this is a new one on me. I am using a Voron 2.4 using ABS.

 

Whenever I slice anything with Cura it is making the prints much larger than they should be. I first experienced this with Cura 5.3 so I tried a previous version and the exact same thing is happening. When the larger prints were coming out I thought it must be a printer fault. But when sliced with Superslicer the dimensions come out correctly. When I view the sliced file in Cura is states that its 30mm on each side as it should be. But when I upload it Mainsail I see the following dimensions. I can't understand where this extra 3.2mm is coming from....

 

Anyone have any idea why this should suddenly be happening?