Cisco 8851 device issues when answering calls

[schwabcm]

We have just finished migrating our campus over to Cisco with roughly 6K 8851 phones.  We have sporadic issues with these phones when answering calls.  Sometimes you have to press the line button for the main line to answer a call and sometimes all you have to do is just pickup the handset.  Our current firmware version is sip88xx.11-0-1-11.  Any idea why this is occuring, I can't believe we would have that many defective sets.

[Andrew West]

Are all the phones configured the same as their are multiple settings on them that can impact call handling?

The phones that sometimes have these anomalies, are they always the same phones?

[m.batts]

This might sound strange but in the past I have had issues with new phones and sticky receivers . i.e when you pickup the handset it doesn't actually go off hook and / or answer the call.

I'm assuming they're all new phones , so often just pushing down and up on the receiver repeatedly  can free them up

[schwabcm]

The scenario we see it most has been when more than one line is on the device, whether shared or an call center agent in their extension mobility profile.  Their profile would have their private line in addition to their agent ID.  So they will get a call on their agent ID when their private line is idol, and they'll have to press the button next to their agent ID in order to take the call.  Simply picking up the handset doesn't always work.

These are all new phones, so I will try pressing the switchhook multiple times to see if that helps to resolve.