Hello Thomas,
the problem is that the user can not reset his password. As a user, I can request an e-mail to reset my password. I also get this e-mail and can open the corresponding page to reset my password with the link from the e-mail. On the page I enter my new password, confirm the password and send the form after confirming the recaptcha. Instead of a success page or just the login page, I get an error page "identity / error" displayed and in the oxtrust.log, is the error message that I have copied in the first post of the post. This message appears in the log but only if you set the log lvl to "debug". Otherwise, at the time of submitting the form, no error message appears in any log of the gluu.