All I can find on that particular error are users saying 'hey, IJ, here's this error. What is it?' And radio silence from IJ's end. Apparently the only (shitty) workaround one user could find was to just copy whatever text they were editing, then pasting it into the same journal entry before saving.
Sorry. Afraid I don't have much I can offer. Maybe a support ticket, just on the off chance?