If you create a list format in Atto and by any reason or accident the starting <ul>-tag is deleted an author can save the changes. The text area is shown incorrect but its not possible to reedit the text. The edit option is invisible. Its required to identify the text field ID to open it again.

The behaviour of TinyMCE is different. Tiny corrects the broken tag by himself while saving changes.

We found this strange behaviour several times on different platforms when authors edited and reeditied text. At first we assumed a problem with cut-and-past from MS Word, but we could create this behaviour in directly added texts.
We assume that this happens also with other broken tags.