Outgoing call, caller not heard

After this config of FreePBX is running well for a number of years, next problem arises.

On all outgoing external calls the caller can’t hear the called person, the called person instead can hear the caller.

Two days ago, when the problem started not all of the external outgoing calls had this problem. Now, all of the outgoing external calls do have this problem.

To exclude that is problem is arisen after updates or changes in config, I restored a two week old backup the VM with FreePBX. But problem still exist.

Further, there is no change in hardware, router-, firewall config etc.

Any help would be appreciated!

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