I have two large C5 user based websites both with around 1100 users and i am getting a extremely large amount of invalid key exception errors in my site logs when users try to reset their passwords.

It seems that both sites are sending out the forgot your password email link. However the UserValidationHash is not being saved. There is a hash being displayed in the email, but this is not getting saved into the database.

Therefore when they attempt to re-set there password they cannot as the key does not exist in the UserValidationHashes table.

I am struggling to re-create the error myself, however i am getting this 4-10 times a day on two websites so something must be astray.

website one concrete5.7.5.3RC1
website two on concrete5.6.3.3

Any ideas would be great, as this is causing our clients a huge headache.

error: "Exception Occurred: /var/www/vhosts/mercedes-benz1team.com/httpdocs/concrete/authentication/concrete/controller.php:227 Invalid Key. Please visit the forgot password page again to have a new key generated. (0)
"