Error Geting Thread Stack (no replies)

Hi all,

We are trying to identify the sentences executed in a thread. I am uing the MySQL Workbench Comertial 6.1.6.

We are trying to use the functionality included on the Client Connections of "View Thread Stack", (we have installed the sys schema throught the Workbench)

For some thread we could gather information, but for other report "Error Getting Thread Stack" "The thread stack for thread **** can´t be loaded, please check if your sys schame is properly installed and available" "Invalid control character at: line 1 column 3072 (char 3072)"

I try to execute the function form the mysql but I gaher a single line:
mysql> SELECT sys.ps_thread_stack(166478, FALSE) AS thread_stack \G
*************************** 1. row ***************************
thread_stack: {"rankdir": "LR","nodesep": "0.10","stack_created": "2014-06-05 12:32:03","mysql_version": "5.6.18-enterprise-commercial-advanced-log","mysql_user": "root@localhost","events": []}
1 row in set (0.06 sec)

I am a new baby in the MySQL world, please, any one could me clarify if this it is a "feature" or a "bug", and if there is another way to identify the sentences executed by a thread.

Thank you in advance, best regards