Cannot clear html formatting in rich text field

I first posted in a similar thread but received no response, so I’ve started a new one. Has anyone ever had any success with formatting in the html tab or using the “clear formatting” tool?

I have a rich text field in my dataset. I accidentally copied & pasted formatted text. I cannot clear the format. See the video for an example. I have tried the following methods:

  1. The “clear format” tool - this seems to work initially, but then the old formatting returns.
  2. Manually deleting html tags in the html tab - this seems to work initially, but then the old formatting returns.
  3. Cutting the html code, pasting into an external editor, removing the html formatting manually and then pasting the html back into the dataset - this seems to work initially, but then the old formatting returns.
  4. exporting the dataset, editing the csv file in Google Sheets (manually deleting html tags), re-importing the csv dataset and deleting the old data - this is the only method that seems to work.
  5. I’ve also tried logging out, clearing cache, removing all website history, re-booting, logging in again, etc.

Has anyone ever had any success with formatting in the html tab or using the “clear formatting” tool? What type of plain text can it cope with? I use BBEdit to save plain text encoded as Unicode UTF-8. If you have has success, please let me know how you did it.