My PC is connected to 10G switch via CAT6 cable. That switch is connected to another 10G switch via fiber cable. The server is connected to the second switch via CAT6 cable.
Both PCs use Aquantia AQN107 NICs. Latest drivers are installed.
I am not a fan of Wi-Fi for many reasons, not the least of which is security.
The second switch also has the 10G cable which runs via internally wired CAT6 through the walls to the downstairs patch panel. That patch panel connects to the router and NTD for Internet access. I am on a 100/40 FTTP fiber connection to the Internet. Though, this is a network issue, not an internet issue.
The server contains all hard drives for content storage. The are two externally connected drives used for backups. One connected via USB 3.0 Gen 1, a 10TB drive which stores all file and folder backups. The other is connected via USB Type C 3.1 Gen 2, a 10TB drive which is used to store image backups.
There are 33 backups run every day, and a few extras for some monthly backups on the 1st and 2nd of each month. Those 33 backups cover multiple file/folder backups of 10 PCs and an image of each PC each day. Two PCs have two images per day, and the server also does an extra backup for my Kodi content.
Yesterday I went to run a special backup of my Mozilla folders (browser and thunderbird email). The mrbak file is 1.7GB. That normally takes less than a minute. It took 9 minutes and killed the network 5 times. Curiously, I restored the data after doing some testing with various versions of Thunderbird and was missing 2 months of emails. Luckily I had also manually copied my email as what got backed up via Macrium was missing a large chunk of email.. Anyway, that's another mystery for later.
Today I am going to copy off 8TB of backups, reformat the drive and copy it back. I'll also run some diagnostics across the drive. I'll also reinstall the drivers on both PCs again, though they are already the latest and have been since Feb. Given manual file copies (in either direction), and image backups are fine, I don't suspect the patch cables. I've also power cycled both switches