Colin,
I would suggest at a minimum you run the 8.21.12 code. You may need to clear your browser cache from time to time when anomalies arise. In the release notes we report all the browsers we test against. Unfortunately we can't test all the patches that get released in between the GA code cycle. If you find something that's reproducible, please feel free to reach out to the GTAC and open a ticket for investigation.
Regards,
Doug Hyde
ESE Extreme Networks
Doug Hyde
Director, Technical Support / Extreme Networks