Yeah, there are definitely other possible reasons. E.g. one workaround I found had Australian users block a specific IP in their firewall. Turns out the DNS configuration was bad, and they were getting an overseas CDN server every now and then. Due to the way the PS4 schedules the downloads (chunks downloaded serially, chunk boundaries at static byte offsets rather than based on time) having even one bad server in the rotation can really ruin performance.

But CDN configuration errors can happen to anyone. I think this client-side mess is a much more creative way to screw up :)