RAXE500 using readyshare cause router to malfunction and causes PC net adapter to give weird errors

Hard to say, though from the way that readyshare is implemented, it may be worth doing a local test on the external hard drive.

Basically if you have another drive with around 4TB or more of free space, then moving 4TB of data to or from the drive, and seeing if it hangs for some time.

One limitation with some routers, is related to how long they will wait for a drive to respond to an IO operation. For example, if a drive if having issues where at certain points, it will struggle to read or write data, the router may not wait long enough for the drive's ECC to respond with the data, especially in cases of drives that do not have a time limited error recovery.

I currently use my RAXE500 with a cheap SATA to USB 3.0 dock, and a 4TB WD Red (CMR) hard drive, and it has worked well with windows backup, as well as copying many large files, and even launching programs saved on the network storage (great for games that store their gamesaves in a subfolder, so far, it has handled tasks like that really well.