Under extrusion with Cura 3.1 I upgraded from Cura 2.7 to 3.1.0 and I'm getting horrible under extrusion, I'm sure this is the software because I rolled back to 2.7 and everything is working fine again.

My printing is a Robo3D R1+ using the "custom FDM printer" profile.

Is there any new setting or a setting that isn't migrated properly that causes this?
Some users have reported upgrades to Cura changing the filament size to the default 2.85&nbsp;mm. If you are using 1.75&nbsp;mm filament (which most printers do), you will get extreme under-extrusion.