Hi @leobrimblecombe,
Thanks so much for sharing a backup! I was able to recreate the behavior you described. It looks like the issue has to do with Specify being unable to construct the Collection Object field format.
In the database currently, there is no table format defined, and this seems to be causing Specify 6 to block creating new objects. The interesting thing about this is that your DataObjFormatters app resource (which captures this format) has not been updated since April 8, 2019, so it’s strange the behavior is just being exhibited now.
In any case, once I modified the Schema Configuration and defined a proper Table Format for the Collection Object table, I was able to save records without any issue.
Can you try to add a field to the table format (e.g. “Leafless”) and see if you are able to save? Thank you!