Can't disable XR500 DHCP server

[grumpy_squirrel]

Router model and DumaOS version:  XR500 V2.3.2.130

I just bought a Firewalla Blue+, which requires my router DHCP server to be disabled for compatibility, so the Firewalla can operate in DHCP mode.  https://help.firewalla.com/hc/en-us/articles/360009401874-Router-Compatibility 

• I log into router's DumaOS > Settings > LAN Setup page, uncheck "Use Router as DHCP Server" and click "Apply". 
• I get a popup window that says "Your devices will be disconnected while the router gets a new IP address." 
• I click "Ok", the LAN Setup pages goes blank.
• I select LAN Setup again and page opens with the "Use Router as DHCP Server" box checked.

I have restarted the router, but the same behavior occurs.  Thanks in advance for any advice and assistance.

[plemans]

You might get more/better help in the proper forum for your device. 

https://community.netgear.com/t5/Nighthawk-Pro-Gaming-Routers/bd-p/en-home-nighthawk-pro-gaming-rout...

the guys on there are super responsive and involved. 

[Netduma-Fraser]

Have you given the device you're changing settings on a reserved IP on the router or the device itself? It's likely done that because you wouldn't be able to access the interface otherwise. Once you've set it then disable it and see if it saves.