[asterisk-users] Asterisk - can't hear other side. Or other side does not hear us

[Ivan Demkovitch]

Hello,
This is not technical post, just looking for suggestions on what to check.I have asterisk for long time, no updates, just maintain OS updates.
I use SPA504G phones
Very rarely and randomly when we pickup a phone - other side does not hear us. Call them back and all works.
Now I have couple people I'm talking to and it seems like very call like this. Someone can't hear someone.
Don't know where to start to troubleshoot and what to look for.
Thanks!
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