Issue in call waiting

Hi, I am new to free pbx, I am getting a issue,
When I call on the extension 237 and agent pick the call, After that no any new call will hit in the queue till 237 disconnects the call. This is only happening with one extension. Some one please help here

You’ve provided very little information here for anyone to be able to help you. What settings do you have set on the queue in question?