Discord Mobile Fails to Assign Roles

In a server I admin with 1000+ members, a few of our moderation staff are having an issue where, on discord mobile (on android) they will give a person roles or remove roles but those changes won't be reflected in the server itself. On their device it looks like it's gone through fine but the changes do not actually occur. This seems to only be happening within the last ~2-3 days. Before then it seems to have been fine.

Edit: The server has been steadily growing, so I don't know whether this has started happening after a certain number of members, or after a certain time/update.