Delay of 45 Seconds with captive portal, DHCP 114 not working correctly

Hi, I have a project to deploy captive portal for public internet access. With all the other devices is working fine (PC/Android/Ipad/Mac) except for IOS devices.

IOS devices takes around 45 seconds to show the Captive Network Assistant (mini browser).

 I am attempting to use the new captive network DHCP advertisement in option 114 as described here: https://developer.apple.com/news/?id=q78sq5rv to reduced this delay.

But It appears that in the first attempt it uses the old method and makes an GET to http://captive.apple.com/hotspot-detect.html. However, if I rejoin the same network a second time (without forgetting the network inbetween) it uses the new DHCP option 114 and opens the captive portal as described in https://developer.apple.com/news/?id=q78sq5rv.

Any idea o what is happening?

I have been seeing the same with CAPPORT testing. First time the page either does not load or loads after some time. All the subsequent attempts work fine.

Delay of 45 Seconds with captive portal, DHCP 114 not working correctly
 
 
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