@Syrak The problem was solved when I convereted the drive to NTFS. Kind of a drag since I'm entirely Mac but it seemed to be the only solution. I now have a new issue with it, which is that I can't...

@Tony The enclosure is a OWC Mercury Elite Pro. Inside is a WD Red drive.

@Tony The drive that does NOT work is 4TB exFAT. The same drive, in the same enclosure, worked when it was formatted HFS+. I had to reformat it since I couldn't write to it when it was formatted HFS+...

@Tony The drive has its own power supply, which it's using. And the router is using the correct power supply as well. I have tried a different external hard drive and the router has no issue. Are...

@Tony I'm having similar problems. My router reboots every 2 minutes, but only when an external USB drive is attached. Without the drive attached the router runs fine. Please advise. Thank you.