We have had reports of Network behaving strangely, eventually a Node stops communicating with the Manager and seems frozen but it is in fact still rendering. The node cannot be stopped from the Monitor either. The solution was to prevent the Anti Virus application (Avast in this case but other AV software may also cause problems) from monitoring the activity of the Maxwell install folder and the temporary folder that mxnetwork uses for network rendering. You can find out where the temporary folder is on a particular node by going to the Node UI and File>Open temp folder.
So please make sure in the AV software to exclude monitoring of the network temp folder and the Maxwell install folder.