Connections drop to zero

[catbref]

After a while, connections drop to zero (or maybe 1) and no new connections are made.

Other symptoms:

• logs only show minimal activity, e.g. only NTP offset adjustments
• Thread dump shows alive, but idle: Controller, BlockMinter, AutoUpdate, network-based PoW thread pool, network broadcast
• Thread dump shows active: NTP
• Thread dump shows only one network EPC (ExecuteProduceConsume) thread, typically blocked at maybeProduceChannelTask

Heap dump shows these odd values:
Network.nextConnectTaskTimestamp and Network.nextBroadcastTimestamp have values way off in the future,
e.g. 1679420975199 which is Tue 21 Mar 2023 17:49:35 GMT

So networking isn't even trying to connect to new peers.