Headset button not working correctly after SP6

[starr]

After 3CX 15.5 SP6 upgrade the headset button on Yealink t48s does not automatically turn back on when hanging up phone handset. With the headset button on we are able to make and receive calls via the headset with no issues. If we place a call using the handset the headset button will NOT automatically light up after hanging phone up.