From Control Panel --> Users – > Users and Organizations click on a User.
Then you have no control to come back to Users list.
Also if you click on Cancel button you stay in User detail
In Tomcat's log you get the below message:
19:20:57,030 WARN [http-apr-80-exec-29][PortalImpl:7503] Unable to impersonate KaUqoR2MbH7Bxp 2uUAmVQ== because the string cannot be decrypted