Weird behaviour: replies show up twice, sometimes. Any ideas how to debug that?

[lostfocus]

Twice this year this happened: I publish a blog post, someone is nice enough to reply to it through ActivityPub and for some reason that reply shows up twice in the database. It doesn't happen all the time - I tried replying to two posts from my Mastodon account and it didn't show the same behaviour.
I'm a bit baffled and unsure where to look for debugging, maybe someone here has a good idea?

[pfefferle]

Sorry for the late reply. This might be a race condition. Because WordPress has no real transaction support, it could result into duplication if the same request is sent twice at almost the same time.

[lostfocus]

Thanks! I'll keep watching it for a while and see if it happens again