None of those items are applicable, I have fiber, Ethernet connected directly to the router and this experience occurs 100 percent of the time. Each and every time I do a scan it begins runs through what appears to be midway through the files and then presents the message that it cannot connect to the server. In spite of this every movie file seems to be properly scanned and updated.
I have the exakt same issue. It has worked great for a long time up until a couple of weeks ago this started showing.
It's the same on both my NUC and my rasp3.
If anyone have a idea what it could be i would be thrilled.