Hi @Stephen_Carver, welcome to the Asana Community Forum 
I suggest reaching out to our Support team with the email addresses of the users in question, along with the project URL link, as our Support team has access to additional tools that we don’t have here on the Community team to be able to look into this further for you.
You can contact our Support team by following these steps: How to contact our Support Team ✉
I hope this helps! 