Confluence is rolling out a new editor. There is currently an Atlassian bug where when editing content in an app macro it sometimes requires a screen refresh to see those changes.
If you are fighting with rendering/usability issues for the new page editor then remember that Atlassian has committed to keeping the old page editor: Atlassian says, "The legacy editor isn't going anywhere"
Error Message
The issue here could be that the colon ":" in the 'page name is what Confluence uses to denote a 'Confluence Space Key".
For example:
A page name could be: "Helpful Information"
A page with that name in another space with space key of "FUN" would be denoted in Confluence as: "FUN:Helpful Information"
In this case "FUN" is the space key. But if the name of the page is acutally "FUN: Helpful Information", then Confluence gets confused.
We are currently looking at a fix for this.
Workaround: If you are able to change the name of the page with the "multiexcerpts" to not have a colon ":" in the pagename, this will all work.
For example changing: "Fun: Helpful Information"
to
"Fun Helpful Information"