I regularly post images to lemmy.world communities but that instance also regularly seemingly fails to actually federate the post on their side.
What do I do when this happens? I can easily tell when it happens, because I can just look at my websites log and see that it isn't being spammed by lemmy requests.
Hmm, I don't have any suggestions for you. db0 outbound federation to lemmy.world hasn't been more than 4 minutes behind in the last 24 hours, and if lemmy.world has received it then it should show. Might need more examples to narrow it down but perhaps @db0@db0@lemmy.dbzer0.com might have an idea.
I think there are sometimes delays. Sometimes I'll post a comment that gets a few replies, which then appear in my inbox, and I'll check each one to mark as read. Then I'll see another new message a few minutes later, but posted before any of the other ones. It'll get listed earlier in my inbox as well so it shows up as an unread message after the couple of read ones I already checked.
Searched for it and it's there. Don't know if it was before but that's one way to "fix" missing content is to use the search feature and paste the original URL