Fop2 stops updating extension status after running for a while

Hi There
We installed FOP2 with freepbx and asterisk, using device/user mode and pjsip.

The issue we are having is the FOP2 stop updating the extension status after a while.

We enabled the debug level to 15, and notice below error
127.0.0.1 <- Event: PresenceStatus
127.0.0.1 <- Privilege: call,all
127.0.0.1 <- Exten: *80176
127.0.0.1 <- Context: ext-local
127.0.0.1 <- Hint: &Custom:DND176
127.0.0.1 <- Status:
127.0.0.1 <- Subtype:
127.0.0.1 <- Message:

127.0.0.1 <- Event: UserEvent
127.0.0.1 <- Privilege: user,all
127.0.0.1 <- Channel: PJSIP/111645-00002905
127.0.0.1 <- ChannelState: 4
127.0.0.1 <- ChannelStateDesc: Ring
127.0.0.1 <- CallerIDNum: 111645
127.0.0.1 <- CallerIDName: device
127.0.0.1 <- ConnectedLineNum: <unknown>
127.0.0.1 <- ConnectedLineName: <unknown>
127.0.0.1 <- Language: en_AU
127.0.0.1 <- AccountCode:
127.0.0.1 <- Context: macro-user-logoff
127.0.0.1 <- Exten: s
127.0.0.1 <- Priority: 3
127.0.0.1 <- Uniqueid: 1527123982.16489
127.0.0.1 <- Linkedid: 1527123982.16489
127.0.0.1 <- UserEvent: UserDeviceRemoved
127.0.0.1 <- Data: 176,111645


127.0.0.1 <- Event: DeviceStateChange
127.0.0.1 <- Privilege: call,all
127.0.0.1 <- Device: Custom:FOLLOWME111645
127.0.0.1 <- State: INVALID

127.0.0.1 <- Event: UserEvent
127.0.0.1 <- Privilege: user,all
127.0.0.1 <- Channel: PJSIP/111645-00002905
127.0.0.1 <- ChannelState: 4
127.0.0.1 <- ChannelStateDesc: Ring
127.0.0.1 <- CallerIDNum: 111645
127.0.0.1 <- CallerIDName: device
127.0.0.1 <- ConnectedLineNum: <unknown>
127.0.0.1 <- ConnectedLineName: <unknown>
127.0.0.1 <- Language: en_AU
127.0.0.1 <- AccountCode:
127.0.0.1 <- Context: macro-user-logoff
127.0.0.1 <- Exten: s
127.0.0.1 <- Priority: 3
127.0.0.1 <- Uniqueid: 1527123982.16489
127.0.0.1 <- Linkedid: 1527123982.16489
127.0.0.1 <- UserEvent: UserDeviceAdded
127.0.0.1 <- Data: 111645,111645

EV: error in callback (ignoring): Can't call method "setQualify" on an undefined value at script/fop2_server.pl line 13036.

Then fop2 stop receiving the AMI event from asterisk, no log in the debug log.

Can you shed some lights on this? Or if you need more information, let me know.