According to this report, the exception occurs on a Data Adapter which is, in turn, a client of some Lightstreamer Server.
This is an architecture which may confuse us; so, before proceeding, please help us better clarify the scenario.
Do you confirm that this Data Adapter (i.e. the one that starts at 04:08:13) opens a client session towards the same Server instance for which it acts as a Remote Adapter?
In other words, do you confirm that there is only one LS Server instance involved?

As we have found out so far, the root cause of your issue is in the Metadata Adapter not responding to the "notifyUser" requests from the Server.
As shown by your "Remote Server" source code, the Metadata Adapter is run by the same process that runs one of your Data Adapters, namely the one that opens ports 7661 and 7662;
hence, according to your adapters.xml file, the "Intraday2" Data Adapter.
May you please specify, with respect to your screenshot, if the "Intraday2" Data Adapter is the one that starts at 04:07:56, at 04:08:02, or at 04:08:13 ?

The next step is enhancing the log, so that we see the DEBUG log of the Metadata Adapter.
Have you tried to configure the log as explained in my previous post, in particular for the executable that runs the Metadata Adapter?
If yes, do you see any DotNetServer.log file? It should be created in the launch directory of the executable.