Hell Anston,
Thank you for the suggestions. I found an alternate current path from another voltage source on our load that was causing the 0.6V on the output of the supply. When I had tested no load, I had not given enough time to let the output capacitors fully discharge, so I was seeing a voltage of 0.3V. This was actually degrading at a rate of around 1mV per 1.5-2 seconds, so I didn't recognize it at first. When I later ran the same test with no load, and ensured the capacitors were discharged, the output voltage was approximately 0V.
In the end, it does turn out to be an issue with our load, and not the power supply design. Thank you for your assistance as I looked into this issue.
Best Regards,
James