In 2.x versions there is no automatic timeout and once a websocket is broken or timed out you get the errors as you mention above (which you can see form the dev tools by pressing F12). You do have options however ranging from if you are running in IIS then changing the timeout of the app pool, but the best i have seen is to use @psDevUK UdTimeout feature which really does work for a generally timeout of the user session. This does not work if the legs are pulled from under the dashboard, i.e a service restart or iisreset.
There is also an enhancement raised for the same timeout functionality on UDv3 to be added to UDv2: Session Timeout Hook · Issue #57 · ironmansoftware/issues · GitHub