OPC-UA client session is disconnecting, why? - by: openventure

I have a windows service that implements an OPC UE client with library version 5.30.

It run for days 24h by day with many opc ue tag subscriptions.

Sometimes I receive a disconnection for an unknown reason and I must restart the service to restore the application

I'm using kepserverex 5.14 as opc ue server.

these are the errors log I had from EasyUAClient.LogEntry.

3/29/2016 8:39:50 AM: OPC Event 0: OPCLabs-UAEngine message:The OPC-UA client session is disconnecting from endpoint URL "opc.tcp://10.74.137.71:49320".
3/29/2016 8:39:50 AM: OPC Event 0: OPCLabs-UAEngine message:The OPC-UA client session has disconnected from endpoint URL "opc.tcp://10.74.137.71:49320".
3/29/2016 8:39:50 AM: OPC Event 0: OPCLabs-UAEngine message:The OPC-UA client session on endpoint URL "opc.tcp://10.74.137.71:49320" failed at tick 588491307 and will retry in 10000 milliseconds.
3/29/2016 8:39:50 AM: OPC Event 0: OPCLabs-UAEngine message:The OPC-UA client session on endpoint URL "opc.tcp://10.74.137.71:49320" failed at tick 588491338 and will retry in 10000 milliseconds.

Do this mean something for someone?
Why I received 2 failed at tick...etc and then I don't receive anything anymore?