I would check out James Dean Designs on YouTube he’s got a good series on the 3018 and uses ugs…
There is nothing wrong with the easel project file it generates out fine i sent it my workbee and 3018 to run in air through easel, ugs and openbuilds and they created the correct size/ shape path… however the feeds and depth per pass are pushing it for a 3018. I would reduce the depth per pass by 70%, the feed by 20% and the plunge rate by 50% and try it again.
Excessive cut settings can result in lost steps, Changing the shape of the actual carve and could change this oval to basically a spiral toolpath.
And my thoughts on why its running in air in ugs, I don’t mean to offend, but this typically occurs when z zero is not set correctly, if probing possibly the thickness is too large in ugs vs actual size, this would set the z zero artificially higher than it should be
Or if your zeroing with paper then the “set zero” button maybe wasn’t pressed, IF this is the case, then it wouldn’t be the first 3018 ive seen running in air this week because the operator forgot to actuator hit set zero button
One more theory (that doesn’t seem to fit if the UGS air carve was actually the right size) is that the grbl settings aren’t right. Specifically the x and y calibration: $100 & $101 so you may want to verify all grbl settings to the 3018 defaults.