Handset stops working intermittently

[ZPM]

FusionPBX 4.4.9
Switch 1.8.7
OS Debian 9
Phone: Yealink T48S firmware 66.84.0.15
Total phones 13


Have a weird issue where it seems everyday intermittently a different phone can no longer use the handset but speakerphone works no problem. So far it happens everyday affecting 1 or 2 phones at the most daily.The result is handset has no dial tone but the phone still works via speakerphone. To work around this you can reboot the phone problem goes away then the next day a different phone has the same exact issue. Anyone ever seen this because I have different environments that have never had this issue.

 

[JamesBorne]

Seems like this issue would be limited to the handset.

Try downgrade the firmware to 83 and see if that helps?
If you provisioned the phone, factory reset, and manually register the phone and see if the issue persists.