I have heard (though haven't tried) that V2 of Compose/Swarm is significantly better.

Anything can and will break. Symptomatically similar thing happened to me with K8s with (IIRC) Calico. And I’ve had issues with Swarm too, although of a different kind (it quietly refused to run a data channel for me over an IPv6-only network, while control channel worked just fine).

It was all quite a while (3-4 years) ago, so I don’t remember much details, except that Swarm was then not exactly capable of working in IPv6-only environments. It was significantly easier to navigate Docker’s codebase than Kubernetes’.

(Ultimately, my solution was that I understood that I didn’t need any kind of orchestration there, just HA/failover. But that’s another story.)