The problems appears to be fixed. 

I rebooted the router and a lot of the DHCP client list cleared out. I'm assuming it's waiting for devices to reconnect before the list fills out. The list does not include all attached devices. The PC I'm writing this on does not show up at this time. However, one that gave me problems does show up. A couple of wireless routers connected as access points, both with fixed IP addresses, do not show up on the DHCP table yet but they appear to work fine. My phone popped up, though. So you can conclude that aspect of the ER605 is not especially robust. Everything works fine, however.

The reboot cleared out the bogus table entries. I have not yet tried to reuse an IP address, however a PC that would not reflect an assigned address now appears to have it.

I can live with the router acting out like this. A reboot appears to clean out the trash entries, although I would prefer simply deleting the entry would be properly reflected in the connected devices table. 

Edit: There is no controller on the system. The router is stand alone.

Edit 2: I reassigned an IP address today. (I'm replacing a file server and changing over from pfSense made me rethink my entire numbering system.) There were no issues. The reboot cleared out the junk. This is still a firmware bug in that deleting a static IP addresses should clear the old and make it available within the firmware without a reboot. I can live with this, but it is a disappointment.