problem

When you edit a segment, and paste here a tag into the segment, then you will get an error.

To reproduce hat error, just copy the following

<1></1>

follow up error JS

This will lead to:
TypeError: undefined is not an object (evaluating 'item.tagName.toLowerCase')

Problem is here that tagName is not an object

follow up error export

Apart from the JS error the content was saved to the DB as unencoded <1> content instead of <1> which would be the expected form