Hi Ashod,
Transaction SU56 contains the user buffer information loaded from the assigned roles. You can view the buffer of the other user using the option as shown below once you enter transaction SU56.
Have you performed ST01 trace while user is executing the transaction. You can see if there are any additional missing authorizations.
Note: Please check if the user is executing in the SAME CLIENT where you have performed the role change. It happens that the user is testing in a different client in the same system.
Regards,
Ravi Kanth.