What causes RTMPT OutOfOrder ?

Prompt >
Prompt > grep -4 OutOf /var/log/wowza/latest.log | head -20
invoke: notFound()

calling subscribe(,XXX,,,true) client amf version = 3 numParams = 8
DEBUG server comment - getClientUpdates: isFirstUpdate: true
DEBUG server comment - RTMPRequestAdapter.service[606075359]: RTMPT OutOfOrder[start]: size:0 seq:2:3
DEBUG server comment - RTMPRequestAdapter.service[606075359]: RTMPT OutOfOrder[stop]: size:1 seq:2:3
DEBUG server comment - RTMPRequestAdapter.service[606075359]: RTMPT OutOfOrder[start]: size:1 seq:3:3
DEBUG server comment - RTMPRequestAdapter.service[606075359]: RTMPT OutOfOrder[stop]: size:1 seq:3:4
DEBUG server comment - Handshake[1]: length:1644
DEBUG server comment - Handshake[2]: length:108
DEBUG server comment - cmd: connect
DEBUG server comment - queryStr:
--
DEBUG server comment - SecureURLParams: connect: SUCCEED (no folder found [/usr/local/WowzaMediaServer/applications/imss/secureurlparams/_definst_], no property found [secureurlparams.connect])
DEBUG server comment - SecureURLParams.onConnect: generate SecureToken GUID
INFO session connect XX.XXX.XXX.XXX -
Client accepted 606075359:
DEBUG server comment - RTMPRequestAdapter.service[606075359]: RTMPT OutOfOrder[start]: size:1 seq:4:4
DEBUG server comment - RTMPRequestAdapter.service[606075359]: RTMPT OutOfOrder[stop]: size:1 seq:4:5
DEBUG server comment - cmd: releaseStream