Unexpected merge behaviour in case of conflict

Reproduction steps:

• Create a new document with the following lines:

  Once upon a time
  a wolf
  started to walk
  in the forest

• Save&View
• Open the page in edit in two tabs and ensure the editor is loaded in both tabs
• In the first tab replace

  started to walk

  by

  dressed in black

  and Save&continue
• In the second tab add

  dressed in black

  line after

  started to walk

  and Save&View

Expected behaviour:

• A conflict is detected

Obtained behaviour:

• The page is saved with a merge and its content is:

  Once upon a time
  a wolf
  dressed in black
  dressed in black
  in the forest