Still cannot build the local music library. It always times out with an error that the share (which it has been working on for the previous 45 minutes) is suddenly no longer available, or that it may have been moved or powered off, which of course is not true.
Tier-1 help desk suggested that I have a double NAT issue. I have a Verizon router with two extenders, and by design, the extenders broadcast the same SSID as the router, and the tech said that was the problem.
My understanding of a double NAT is that you have two or more devices providing network address translation for outgoing requests, and one way to detect it was through traceroute:
traceroute google.com
traceroute to google.com (142.251.40.238), 64 hops max, 40 byte packets
1 cr1000a (192.168.1.1) 3.594 ms 3.011 ms 2.882 ms
2 lo0-100.washdc-vfttp-366.verizon-gni.net (71.178.216.1) 17.840 ms 9.364 ms 19.354 ms
3 * * *
A double NAT would show a private IP as the first two hops, but here there is clearly only one.
Could duplicate SSID names cause a problem? And why would SSIDs or double NATs cause a local music library rebuild to fail?