I have a similar problem, I sent my old passport and my residence permit (colorful photocopy, the website said it could be photocopied if the proof was a residence permit) to the Durham office, a week later they received it, and another week Later they told me that some proof of residence from my country was missing (but I already sent it to them) and just a minute later I received an email from them asking someone to confirm my identity… I don’t know what to do, I’m going to ask someone to confirm my identity but I don’t know if I should ignore the message of the proof of residence that according to them is missing, because the tracking website is only asking for the confirmation of identity by another person, but the email I received before that left me worried .