NextDNS Connectivity Issues on iOS and iPadOS

I have several devices in my household running Windows, macOS, Android, and iOS/iPadOS, and all of them are configured to use NextDNS. However, I have been experiencing persistent issues specifically on my iPhone and iPad.

I noticed this last month, and I turned off ultra-low dns setting in the app which seemed to work, but they have removed that option with the new update today.

Safari pages have stop loading, chat apps stop refreshing, and videos fail to stream. The only way to restore connectivity is to disable NextDNS, after which the internet works again immediately.

I have already tested both the NextDNS profile generator and the NextDNS app, but neither resolved the issue. Since the same setup works fine on my other devices, I do not think the problem is with my ISP or Wi-Fi network. I don't understand why network connectivity on iOS is so tricky for NextDNS. 

My current suspicion is that iOS/iPadOS may be trying to use different ports or behaviours that are being blocked somehow, but I am not sure how to confirm that. I'm wondering if anyone has experienced this and was able to solve it.