I have the same unit, and I agree, it’s pretty mediocre.

One thing I learned about reserved addresses - they MUST be within the DHCP lease range.  If you have them outside of the range (which of course is what everyone normally wants), then when the lease time expires, the reserved address is dropped, and a new one is supplied from the DHCP lease range.  So, in effect, your desired address is not really reserved!!!

One of many other problems is that the client list is often missing entries.  Every time you refresh the page, you get a different list of clients.  No apparent pattern, as far as I can tell.