Yealink T46S & T46G one way audio intermittent issue

[Byron13]

Hi All,
we have a fleet of T46G & T46S, in our environment.

SFB on prem and EICC (Touchpoint) customer service portal.

When customer service take a call from and try to do a consult transfer to the Yealink (end user phone), the phone rings, when answered the end person on the Yealink can hear the operator, but the operator cannot hear any audio from the Yealink.

If they hang up and try a second time, 9/10 audio is established both ways and the call is completed fine.

We have tried multiple Yealink phones, with varying levels of firmware. Also tried the latest firmware. This is an intermittent issue, and most of the time it's the first call has one way audio.

I have verified if transferring to a Jabra over ear headset or HP4120 Lync/SFB phone the calls connect 10/10.

The Touchpoint EICC software just creates a conference call apparently, nothing else is special.

Is there known issues with conference calls with Yealink's. Also does the phone go to some kind of sleep mode, that's why the second call seems to connect once it been woken up if it's been idle for a while.

Any help/suggestions would be appreciated. Don't really want to have to change our fleet of Yealink phones out because of this issue.

Regards.

Brendon.