Asterisk 11 NOTIFY/BLF Lights

Hello,

We are running asterisk 11.3 and for some reason after a period of time, the BLF lights on phones subscribed to extensions hints stop working. In the asterisk CLI, it shows that requests sent to some (but not necessarily all) watching extensions are “queued”

Example:
Extension Changed 100[witgoffice-local] new state Ringing for Notify User witg_110 (queued)

Network trace shows that no SIP Notify is sent once an extension goes in to “queued” state and the extension never comes out of “queued” state. The only way to get it to work again is to make the extension go offline and back online again.

Extensions that do not have queued listed in the notifications continue to work normally (BLF lights show correct status).

Has anyone seen this behavior before? is this a configuration issue or an asterisk bug?

Thanks,