It has come to our attention that some users have been experiencing a delay in loading captive portals on Apple devices. The said delay sometimes takes up to a minute. This behavior has been observed on devices that are on iOS 12. It was also observed that there is no issue on other iOS devices that are on earlier versions, Android, OSX, and Windows devices.
According to Apple forum discussions, Apple has been informed and has acknowledged the issue. Although it has not been confirmed officially by Apple, sources say that it has been partially fixed in iOS 12.4 Beta 3 and additional fixes are expected in iOS 13. iOS 12.4 is expected to be out in a month, and iOS 13 in the Fall.
We shall update this post when the fix is in.