only happens to agents that connect to a single vicidial campaign
I hope this means "it only happens on one campaign" and NOT that you are connecting agents to multiple campaigns simultaneously.
The address of the campaign at the network level was changed
I'm not sure what this means. Please elaborate if you can.
The equipment is on a LAN network, in this case there would be no instability in the network
That is not a valid assumption. Local switches die, too. And if you have a physical location associated with that "one campaign" ... one dude kicking a network wire when he's bored can be a humorous outcome (expensive, but humorous).
The google drive image is a dead link.
It sounds more like your browser is crashing, which could be related to another tab open doing something else. Do these agents log in to another site to work on this campaign?