Hi There!   We had similar problems, using Cisco VoIP phones.. 7921, 7925, 8821.. no one work well after we update version on APs. I mean, we had good performance on 25.9, but when we update on 25.11, we lost that good performance on VoIP phones. after a 10, 15 secs, we lost voice on phones, we saw the dashboard, we could see good level and equipment connected, but no service.    At the end, we found version problems, so we made a downgrade, we returned from 25.11 to 25.9.   We are using APs MR42 and MR52.    Now, net IP voice is working very well on 5 GHz Band. ... View more