Call Disconnects on Yealink T26P

[ykpasupulati]

We have recently replaced all our phones with Yealink T26P from Polycom IP331.

Here is the details of the setup.

Asterisk 1.4.21.2
Yealink T26P with 6.61.0.83

Now we have issue with simultaneous calls. When two incoming calls come in, called is unable to hear the caller and call gets dropped.

If I disable the call waiting on each extension on asterisk, the calling works fine but the users are unable to quickly pickup the calls, if they are in call and then hangup the call.

This same scenario worked with Polycom IP331s. So I am not sure what is causing this issue.

Is this a configuration issue or the issue on the T26P? Can Yealink help fix this issue?

Any help is appreciated.

Yogi