[@iamthewebb Participant 6 years, 7 months ago]

Are they doing the same as what I just did and attempting to login from your forum pages that only accept a username, where as your main site login page accepts an email address or username?
For help with this you will need to get the users to explain step by step each thing they do when the error occurs so it can be replicated.
If they are doing things correctly and it randomly doesn’t work you should also be experiencing the problems.