Changing DHCP settings cause Wi-Fi to turn off

[A123456]

I’m setting a device to a static IP address and every time I click on apply changes in the DHCP settings the Wi-Fi switches off. 
I had it set on my previous router. Engineer changed my router yesterday to a Hub 3.0. The device has the IP in its settings, I’ve been using it for 2 years.
I logged into my router, got the IP the device is on, set it to the IP I want (not in use by anything else) and set the rule. All ok until I click apply changes, that’s when the Wi-Fi switches off. I’ve tried it on 5g & 2.4g, both switch off. Does anyone have any suggestions? 

I will also be using port forwarding with this static IP. 

[legacy1]

Its time to use your own router with 1Gb ports and put the hub in modem mode.

[Adduxi]

Is this the WiFi on the Hub disables, or the WiFi on the device stops working? 

[A123456]

Hi, thanks for replying. 
I’ve run a test and it’s the wi-fi at the hub that goes off, not just the device. 
I can now successfully ping the static IP address of my device but can’t SSH into it like I did previously. Despite the wi-fi switching off, it seems to have eventually done what I wanted it to do, the problem may now lie elsewhere. 

[A123456]

I don’t want to do that and although it still switches off when I make any changes to DHCP, it seems to have, finally, accepted the rule.

[Client62]

I'd not noticed the WiFi out.

Could it be the Hub 3 is expiring all the DHCP IP leases, prior to re-starting the DHCP server with the revised Reserved IP Addresses list.

From a previous post entering a Hub 3 Reserved IP Addresses had failed to work due to the browser. I'm suspecting the Chrome browser.

Using Firefox we can manage the Reserved IP Addresses without issues.

[A123456]

Hi, thanks for the reply. 
yes, I’m using chrome browser. It didn’t occur to me I could be a browser issue! I’ll try a different browser.