Inter-service communication failures with 1.12.1 on Ubuntu 16.04.1

Has anyone else seen situations like this:

On node 0, I have services “a” and “b” each trying to connect to service “c” on node 1.

I’ve seen several cases where, after restarting service “a”, it can’t connect to “c” but service “b” still can. “a” and “b” are on the same node and on the same virtual networks and one can reach “c” but not the other.

Deleting and recreating any combination of “a”, “b” or “c” didn’t help; I had to remove all services and overlay networks and recreate them all.