Per few arwiki user complaints that when he try to paste wikitext on new wikitext mode (2017 wikitext editor) and choose (Convert to wikitext) it fails and paste it as plain text.

Steps:

• Enable New wikitext mode from beta features section.
• Before open wikitext editor> Copy any wikitext (e.g include internal links)
• Open wikitext editor> try to paste the wikitext
• Will face question "Convert formatting to wikitext?"
  • Convert to wikitext OR
  • Use plain text
• Choose "Convert to wikitext" then it fails and paste it as plain text (as you choose "Use plain text")

Don't know if it related to T255785