On Asterisk, we have declared queue as : [myqueue] (in lowercase)
In buttons.cfg, this queue is declared as : [QUEUE/myqueue]

Adding an extension (ex: SIP/200) to this queue is working fine but when we want to remove this extension from the right queue panel, we've got an error.
Here is the debug :
<= <msg data="QUEUE/MYQUEUE|queuelogout|SIP/200|.......>

As you can see, MYQUEUE is in UPPERCASE so asterisk can't find this queue:
(Message: Unable to remove interface from queue: No such queue)

If we remove SIP/200 not from the right queue panel but directly from the SIP/200 button, this is working fine. myqueue is written in lowercase:
<= <msg data="myqueue|queuelogout|1|.....

Cheers