"Wiki" insert gives unhelpful error. What's wrong?

[Benjamin Griffin]

This is using the Atlassian hosted Confluence, on a Mac (Sierra), in Firefox (58).

Test content: screenshot before "insert"

And error: screenshot after pushing "insert"

The content works in the "preview" pane, but will not "insert" because of unspecified errors.

[Benjamin Griffin]

Any help, anyone? Does it help to include the error message as text?

"Wiki markup conversion errors

:

"

Nothing else. Complete input shown in "before" screenshot. It was 12 lines or so.