System Error message when trying to edit an email

We are running a standard 12 email nurture campaign. I have been able to edit 9 of the 12 emails. However, on 3 of them, I get the below message and cannot make edits.

I have tried all the standard 'quick fixes' (refreshing, logging in and out, trying different browsers, etc.) but still get the message.

Does anyone have any ideas? (Will submit a support case, but was hoping there was something I could do on my end first).

Thanks!

Tim