Hey Mark,
Thanks for reaching out to us!
To clarify, this is occurring on the event edit screens in the Venue metabox? I did a couple of tests on my local install but wasn’t able to replicate this issue (although you did mention that some of the issues were sporadic so I’ll try a few more times).
However, as a first step, have you tried following our Testing for Conflicts procedures to ensure there isn’t a conflict occurring with an existing plugin or theme.
Let me know if that reveals anything different.
Thanks!