Handsets not ringing for incoming calls

[justin.rampy@ringcentral.com]

I work for a cloud hosted PBX provider and we recently started selling the Yealink W52P with multiple handsets. I have a customer with the same issue using 4 handsets and have loaded the latest available firmware for both the base and the handsets as follows:
Base Firmware: 25.73.0.22
Handset Firmware: 26.73.0.12

The jury is out so far with my customer as we did this upgrade on 11-14-2014 and today is 11-17-2014. However, I can tell you from my lab phone using 3 handsets and the same above firmware loads, I have replicated the following results:
Result 1: Handset 1 did not ring on the first ring cadence but starting ringing in sequence with the other 2 handsets on the second ring cadence.

Result 2: Handset 3 did not ring for the first 2 ring cadences but then started ringing in sequence with the other 2 handsets on the third ring cadence.

I don't believe this to be environmental in nature as I can replicate these results no matter how far the handsets are from the base unit. I recommend that everyone with this issue validate if the handsets start ringing after a certain number of ring cadences. This has been my experience with this latest firmware, all the handsets will start ringing after 1 or more ring cadences. If that is also your experience, it is important to include that detail in the problem description. I would call this an intermittent "delayed ringing" of all handsets. If the handset(s) in question truly do not ring at all, that is different than what I am able to reproduce. Either way, this is definitely between the base unit and the handsets.