LoggedUserId inconsistency

Im trying to get FirstName, LastName and Password from a current user. Im using LoggedUserId.value to get his ID. but only worked one time. In Bonita Engine Log appers this:
"depends on loggedUserId is neither defined in the script nor in dependencies."
or sometimes appears:.
"groovy.lang.MissingPropertyException: No such property: loggedUserId for class: Script1".