Multi selects clearing when editing form

I have an object with two multi selects (venue & people)

When creating the object I have no issue with filling my multi selects- venue and people.

When editing the object I add a venue, then when I add a person it clears out any changes I've made in the venue multiselect.

In short- when editing any unsaved data in the multiselect gets cleared when I edit another multiselect field.

Any suggestions on what I'm doing wrong??

PS. I have created a new Business Space and its still happening!

Nick

Please send us a small BSV that reproduces the problem and describe what needs to be done to reproduce it starting from blank data.