Some operations in the User Manager dialog may be slow or even fail by timeout if performed by a non-admin user. For example, members of the Sitecore Client Account Managing role might be affected. Operations like editing the information about a user, changing a user's password, or unlocking a user may take an unreasonable amount of time or even fail by timeout.
To resolve the issue, consider one of the following options:
Alternatively, you can perform operations in the User Manager as an administrator.