I run Syncthing 1.20.1 on Linux.

I notice, when I use quic with NAT traversal via STUN, that after putting the host into suspend mode (S3) for a prolonged time, no new quic connections are established. When I look for the entry on the discosrv, the host inserts again the previous remote/NAT'ed IP/port which it had before the suspend. More often than not these are not correct anymore, of course.

Looking around a bit in the code, I understand the logic here, such that no STUN servers are contacted again, as long as there is traffic on the local port. As the peer still has a quic address advertised, there will be (only outgoing) traffic to try to reestablish a connection. Thus the discovery address is never updated and the firewall of the peer remains closed, as it tries to contact only the old address.