4
I don't know what the solution might be, but, a temporary workaround came to mind if you are pressed for time.
Are you able to create a new custom block? (If you can't, that still would be good to know, as people try to assist with troubleshooting).
If you can create a new custom block, try copying the old disclaimer into a new block. If the disclaimer is mostly straight text, you should be able to pull up the disclaimer in your web browser from your site. If it is HTML instead, you can view source and copy the relevant part into your new custom block.
I know that's not ideal, but, when you are pressed for time, sometimes a workaround is in order.
Hope that helps.