what is "isession_handle_evt" log?

hi all,

i have two BIG-IP APM and they are working as Active-Standby.

last month, i upgraded BIG-IP APM from TMOS v10 to TMOS v11.

after upgrade, BIG-IP APM shown some log messages in /var/log/ltm:

May  3 17:03:14 vpn1-1 err tmm[17077]: 01470000:3: iSession: Connection error: isession_handle_evt:6721: isession_handle_evt: bad transition:7
May  3 19:13:25 vpn1-1 err tmm[17077]: 01470000:3: iSession: Connection error: isession_handle_evt:6721: isession_handle_evt: bad transition:7
May  3 19:34:33 vpn1-1 err tmm3[17077]: 01470000:3: iSession: Connection error: isession_handle_evt:6721: isession_handle_evt: bad transition:7
May  3 19:44:30 vpn1-1 err tmm3[17077]: 01470000:3: iSession: Connection error: isession_handle_evt:6721: isession_handle_evt: bad transition:7

what does it mean and does it effective to BIG-IP?