I had a similar issue with the T-28on a V12 sp6 system.
Updated the T-28 with the firmware version that the 3CX system provided. After having done so, the extensions in the queue would no longer ring (ring all strategy), but would if dialed directly. The folks started to monitor the BLF light to see when ringing from the queue so they could answer. Like you, I ended up having to revert the firmware. The version that was offered was 2.73.0.40. The latest on the Yealink site is 2.73.0.50 and the one that I reverted to is 2.71.1.1.
What is really frustrating is the Yealink has a bug that apparently limits the PC port to 10Mbs despite it being set to 100Mbs in the T2X series. It drove a client in Pennsylvania bonkers as to why their 30Mbs connection never seemed to get over 10Mbs. The release notes indicate that this is fixed when moving to 2.72.0.1, which was released in Dec.2013. The Yealink site still shows the 2.71.1.1 as the approved 3CX version.
Will submit a ticket as well.