Losing chat messages when chat.typing-isenabled=true

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In a chat conversation, some chat messages are not sent from the agent to the customer and the customer sees that the agent is still typing. The opposite happens also. That happens when chat.typing-isenabled=true in IW application in CME ( regardless the value of send-typing-notice-back in chat server ). When i set both to false then it works ok but the customer cannot get the "agent is typing" notification.

What is the root cause here?