Returning users logged as new users


We have just upgraded to 3.13.0, and since the upgrade all users (returning & new) are logged in as new users with new user ids.

we set the user ID in the tracking code using the login email, our website is behind SSO so no user can actually visit the website before logging in.

is there a chance that the function that calculates the user hash has changed, any thoughts?

Many thanks,