Just tried, both with confbridge and meetme, and I cannot reproduce anything. Talker detection works fine and is shown correctly on conference buttons. To get you an idea of the events that modify the participant talking icon, you can look at those when you run fop2_server in debug level 1 mode at least:
127.0.0.1 <- Event: MeetmeTalking
127.0.0.1 <- Privilege: call,all
127.0.0.1 <- Meetme: 5000
127.0.0.1 <- Channel: PJSIP/309-0000000b
127.0.0.1 <- ChannelState: 6
127.0.0.1 <- ChannelStateDesc: Up
127.0.0.1 <- CallerIDNum: 609
127.0.0.1 <- CallerIDName: Maria
127.0.0.1 <- ConnectedLineNum: <unknown>
127.0.0.1 <- ConnectedLineName: <unknown>
127.0.0.1 <- AccountCode:
127.0.0.1 <- Context: from-internal
127.0.0.1 <- Exten: STARTMEETME
127.0.0.1 <- Priority: 4
127.0.0.1 <- Uniqueid: 1425640211.99
127.0.0.1 <- Status: on
127.0.0.1 <- User: 2
127.0.0.1 <- Event: MeetmeTalking
127.0.0.1 <- Privilege: call,all
127.0.0.1 <- Meetme: 5000
127.0.0.1 <- Channel: PJSIP/309-0000000b
127.0.0.1 <- ChannelState: 6
127.0.0.1 <- ChannelStateDesc: Up
127.0.0.1 <- CallerIDNum: 609
127.0.0.1 <- CallerIDName: Maria
127.0.0.1 <- ConnectedLineNum: <unknown>
127.0.0.1 <- ConnectedLineName: <unknown>
127.0.0.1 <- AccountCode:
127.0.0.1 <- Context: from-internal
127.0.0.1 <- Exten: STARTMEETME
127.0.0.1 <- Priority: 4
127.0.0.1 <- Uniqueid: 1425640211.99
127.0.0.1 <- Status: off
127.0.0.1 <- User: 2
127.0.0.1 <- Duration: 1
Regarding the dialed number, not sure where are you seeing 'dstring' or 'out', but those come from your own dialplan broadcasted via AMI events. As the manager changed, perhaps the actual numbers are not shown on the same headers as before.
However, dialing locally into a conference on my test system worked well, but I am dialing the conference locally, not from a DID or external numbers.
In any case, I cannot do anything without having access to the debug level 1 from fop2_server, to inspect the manager events you are receiving.
Best regards,