Issues with Trello on iOS

I recently noticed that I couldn't pull down the latest Notifications in the Trello app on my iPhone. Errors logged by the Trello app are pretty vague, just a general 'network cache/timeout error' sort of thing. Strangely the app works fine otherwise: I can add/edit/delete cards etc. just fine. 

After some diagnosis work it became clear that NextDNS is somehow the root of the problem.  When disabled everything works fine. 

I've been experimenting with the Allowlist to see if any particular domains that the app contacts might be related, but either that's not the actual problem or I haven't found the right domain (and anyway nothing was listed as blocked at the time of my testing). 

Has anyone else seen this? Is there some other configurational change on NextDNS that might help? Could it somehow be a bug? Or something Trello is doing 'wrong'?

Cheers.