Some channels cannot create new conversations

There is a Team with multiple channels for an event, and some channels simply get stuck when trying to post a new conversation. This happens with guest accounts and members, and only on certain channels. The only person that can post is the creator of the channel.

It's not a permission issue since the channel where it's disabled doesn't allow conversations to be posted. The problematic channels get stuck on Sending...

It seems to be server-side, but any help would be appreciated