1 image has not been indexed

[cameronreilly 16]

I'm getting the white on red exclamation mark on one of my notes indicating that it hasn't synchronized and I suspect it's something to do with one of my images which might be too large for the size limits. But which image? This particular note has a dozen screenshots inside it. How do I know which one is the offender? Should I delete theme one by one and try to sync   ? Is there a better way?

[cameronreilly 16]

I took out all of the images, optimised them individually, and put them back into the note. Now the filesize of the note is only 4.2 MB, but it's still not synchronizing. And I looked up a support email from earlier this year where I was told that the size limit for a note is 5 MB for the TEXT and that doesn't include attachments, which I assume includes images. So I have no idea why this note isn't synching.

[cameronreilly 16]

Now I'm getting another error message: "The content is invalid". WTF does that mean?