Access Control - Nighthawk RS600 "Whack-a-mole"

Router Firmware Version V1.0.5.12

I am using a Nighthawk RS600 along with a BE5000 (version EXS27 firmware v1.0.1.34) WiFi Extender. The issue that I am running into is that when I turn on Access Control > Block all new devices from connecting, a number of devices that I have set to allowed automatically switch back to Blocked.

Example:

1. Wireless TV and Xbox One are currently set to 'Allowed'. The Extender is listed as 'blocked'.
2. In Access Control, I set the Extender to 'Allowed'.
3. Upon applying this new setting, the status of the Wireless TV and Xbox One automatically swap to 'blocked'.
4. In Access Control, I set the Wireless TV and Xbox One to 'Allowed'
5. Upon applying new setting, the status of the Extender automatically swaps to 'blocked'

The Extender has a fixed IP address and the TV and Xbox have status IP addresses. We have other devices attached to our router and they are listed in the Access Control which do not seem to be affected, however, these few devices seem to be the ones with the issue of playing "Whack-a-mole" trying to keep them all set to "Allowed" at the same time.

Is there a reason that the router's Access Control does not keep the "Allowed" status that I set? a conflict of some sort?