Performance issues 8128 caused by firmware

[daanvk]

We have deployed a number of 8128 devices in our office and face some performance issues.
We first looked at out wifi network, but nothing seems wrong there. Our network vendor asked us to update the firmware on the phones now to see if that helpes. We are currently on 2.6.6 2012-06-04, does this firmware cause issues?

Where would I be able to get the latest firmware? We have a cradle to perform the update.
Is there any concern to update one phone to make some tests?