Keep alive request fail|OPC UA Implementation: Stacks, Tools, and Samples|Forum|OPC Foundation

Hi, I have a problem with OPC UA connection that I cannot resolve it.

The client application is running on the same server as OPC server (kepware).

Parameters are;

for session;

KeepAlive = 1000 , Lifetimecount = 5000

for subscriptions;

subscription = new Subscription()
{
PublishingInterval = 50,
PublishingEnabled = true,
KeepAliveCount = 1000,
LifetimeCount = 5000,
MaxNotificationsPerPublish = 0,
DisplayName = m_ConnectionType.ToString(),
MaxMessageCount = int.MaxValue,
MinLifetimeInterval = 1000,
DisableMonitoredItemCache = false,
TimestampsToReturn = TimestampsToReturn.Both,
FastDataChangeCallback = new FastDataChangeNotificationEventHandler(fastChange)
};

The error happens at "keep alive requests";

BadNoCommunication 'Server not responding to keep alive requests.'

I cannot reproduce this issue, it happens now and then.. there is no issue on reconnection, it works.. but I lose data during reconnection process.