What is "[WIP] CID NOT FOUND[5]"?

I am creating an application for UDP communication in 3G network.
Sometimes, Trace log “[5] [WIP] CID NOT FOUND” is output, and can not do UDP communication.
Why does “[5] [WIP] CID NOT FOUND” occur and how should I do?
Also, is there a way that the application detects the “[5] [WIP] CID NOT FOUND”.

My development environment is following.
LSI of communication unit : SL8084T
Open AT Application Framework package : 2.50.0.A1.201302131145
Internet Library Package : 5.53.0.A1.201211071132


It seems to be network related and happens during network lost or cell change.

Could you please set AT+CGREG=2 and monitor the unsolicited +CGREG notification?
Also, does it happens in a moving vehicle?