Inconsistent USB Storage Connection

I have two Macs that I want to set up with automatic Time Machine backups over WiFi. I used to do this with an Apple Time Capsule, no problem.

I have two hard drives in an IcyRAID enlcosure (MB662U3-2S R1) that I want to use. I have been able to connect the computers to these drives using the provided instructions with the router manual.

However, the drives keep disappearing off the network and I have to go in and physically disconnect the cable and reconnect it to get them to come back.

When I do this, the drive letter seem to changing at random, so I have to connect to a different drive every time. (i.e. one time it's G, the time it'll be F, the next time it'll be P)

As if this wasn't frustrating enough, the router dashboard sees 4 drives, even though there are only 3 on the network - one built in to the router (200 MB) and the two in my IcyRAID enclosure (4TB and 2TB). 2 of these drives share the same letter every time and, you guessed it, they're the 4TB and the 200MB drives. When I try to connect to the 4TB drive, I can now only get the 200MB one, so even though the router knows it's there, I can't connect to it.

This is the case whether I am using AFP or SMB to connect.

So, three questions.

1 - How can I get the router to differentiate between the drives properly?

2 - How can I get the drive/share name to stop changing?

3 - How can I keep the drives/shares available all the time?

Any help would be much appreciated.