The names are part of the network addresses, for example: SMB://Archer_D7/volume(sda1)/music. So when the name of a volume changes (from sda1 to sdb1, for example) addresses become invalid.

As you can see, the drives have changed addresses between reboots. As to investigating what happens if drives are connected directly to the D7 rather than via a hub, as I can't connect three drives...

Model : Hardware Version : Firmware Version : ISP : Three USB drives are connected to a TP-Link Archer D7 via a hub: "Drive 1", "Drive 2" and "Drive 3". If I boot the D7, it might share the drives...