Lost voice on SIP trunk bridges

I have a situation where two remote calls are bridged and they lose voice (can’t hear each other).

We initiate a manual call out of a SIP trunk, person picks up. We put them on hold, dial a second person on a second line using the same SIP trunk, second person picks up. We transfer line 1 to line 2 (tried on Granstream and Polycom phones) and the two lines are joined in a basic mixing bridge (can see via ARI) but neither one can hear the other.

I’ve tested several settings changes thinking it’s the SIP trunk - but nothing there seems to affect this.

Anyone run into this?

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I had posted this to the wrong thread, and was unrelated to the issue described.

Ok - we’ve replicated this simply by placing two outbound calls from the same phone, then transferring one to the other… Both Grandstream and Polycom.

Can’t figure this out. I suspect it’s something with the trunk config.

make sure you have neither directmedia = yes nor canreinvite = yes in the trunk settings