How to delete a DUNDI trunk in FreePBX?

Question

Asterisk

The problem is the following.
There are three asterisk 11 servers with the FreePBX(2.11) shell; these three servers are interconnected via DUNDi. Asterisk 1st, asterisk 2nd and asterisk 3rd.
Asterisk 1st resolves internal calls - between the second and third asterisks and also directs external calls to internal subscribers on the 2nd and 3rd.
Queues are created on the first and second asterisks, the third one is empty without queues.
There was a problem: subscribers from the 3rd asterisk could not get through to the queues that were created on the second asterisk.
In the end, I decided to kill the queues on the second aster and create them on one per 1m so that everyone can call without problems.
I deleted the queue on the 2nd asterisk and went to create this queue on the first asterisk, but this aster does not allow me to create it.
Writes -

Extension 911 not available, it is currently used by DUNDi: 10.50.70.200/911 (EXISTS).

.
I have already turned both of these asterisks upside down, I just can’t find where it is written. Even grep didn't find anything.
If anyone has come across this problem. Kindly advise.