I've had exactly the same issue for 2 years and I have narrowed it to dropped packets on the network. I'm connected to internet through WiFi bridge that period

I've had exactly the same issue for 2 years and I have narrowed it to dropped packets on the network. I'm connected to internet through WiFi bridge that periodically has transmission issues (over 200 meters distance) and if average amount of transmitted packets (I can see it in antenna panel) is anything else then 100% and negotiated speed is anything lower than maximum 54 Mbps then neither Safari nor Firefox will be reliable and I will get "connection reset by peer" error that will go away after refresh. Chromium-based browsers work fine, I'm using Vivaldi with no issues. On Windows tools like curl and wget work with no issues but not on macOS - it looks like a deeper problem with its network stack that Chromium browsers somehow avoid. It might be a correlation without casualization, but I also was unable to find a good way to debug this issue.