>Are you using packet encryption or VPN? I've seen Router firewall rules blocking access if you're using UDP encrypted packets. Sometimes all good until improving fiber performance pushes past the rule's limit. In my case, router logs revealed UDP packets blocked once they reached maybe 100mbps, reducing transfer to a crawl. It can be prevented by increasing Denial of Service default counters at the router, but that exposes to more risk of DOS. Change to TCP packets= all good.

Thanks