ZNC is great for having a persistent IRC connection, but it’s not so great when the IRC server or network has a blip. Then you can end up failing to rejoin with

over and over again.

The way to fix this is to limit the number of channels ZNC can connect to simultaneously. In the Web UI, you change ‘Max Joins’ preference to something like 5. In the config file use ‘MaxJoins = 5’ in a <User foo> block.