I have a client that is using an ActiveGate for several extensions. This ActiveGate runs on Windows, and has had several problems with extensions in the past. Despite looking at the logs, the errors would show some strange messages, and I was unable to detect the problem till today, in the past blaming the issue probably on some strange Windows configuration ☹️
I would thank @AliSaeed for raising awareness to the root cause of the problem to me, on one of my own extensions: https://community.dynatrace.com/t5/Extensions/Ping-Every-Second-Extension-Error/td-p/199622
I then associated this with the extensions having problems on this server. Indeed, it seems that a lot of ActiveGate extensions seem to be making the same mistake as my own: hard-wiring the TCP 9999 port into the extension, as it is the usual port on which ActiveGate listens.
If you have changed the 9999 TCP port on ActiveGate, you are probably having problems with this configuration, if you are using ActiveGate extensions. If it's the case, it's probably good to check if this might be the cause...