Diagional Oval Circles

After recently upgrading my TS2 to the larger extension i have discovered i can no longer make perfect circles.
I have gone round and round (pun intended) with belt tension even as far as the tilt test to make sure that it can move on it’s own still. I have tried a different software package and got the same result.
I’m incredibly new to this world and would ask for patience with settings if we suspect that is something that could cause this. the only item i have changed from the installation file to program the TS2 for lightburn is the dimensions of the table. (could this be an issue?)