Could not run Append to Note, Problem communicating with the app

Hello, I’m writing a shortcut which will harvest my highlights from Readwise and put them in a Apple Notes. (Readwise has integration with Evernote, Roam, and Notion; but I have my brain in apple notes!)

My shortcut hit’s two API and then creates or appends my highlights to and existing note, or creates (and then appends the highlights to) a new note. About 10% it works great! The rest of the time it will fail on the second, third, or fourth note being appended, with the error message: “Could not run Append to Note: There was a problem communicating with the app.”

I’ve googled and search the usual communities without finding a solution.

Does anyone have ideas?