@dc42 Thank you for the amazingly quick response! The firmware binary fixed the kinematic issue.
Still lots of tuning and tweaking to do but the kinematics seem to be working correctly now.
Here's a short video showing what polar's do best, printing vases: https://drive.google.com/open?id=1T2Wjb3OejqWlkfOUjZREdYk8xY59UvRD
@fcwilt My homing files are the same as outlined in the polar setup guide: https://duet3d.dozuki.com/Wiki/ConfiguringRepRapFirmwarePolarPrinter