Issue with syncing Comments of a Comment

Hi, I have a weird behaviour of Syncing Comments. According to the Troubleshoot section for testing synchronisation, it should be possible to retrieve comments via:

curl -H "Accept: application/activity+json" https://your-instance.com/comment/123 # the id of a local comment

That works for Comments which are direct responses to a post, e.g. The response https://lemmy.ml/post/421708/comment/253216 (shortcut url: https://lemmy.rimkus.it/comment/1701) can be successfully retrieved via:

curl -H "Accept: application/activity+json" https://lemmy.rimkus.it/comment/1701

But The Answer Comment to that Comment: https://lemmy.ml/post/421708/comment/253238 (Shortcut url: https://lemmy.ml/comment/253238) can not be retrieved via :

curl -H "Accept: application/activity+json" https://lemmy.ml/comment/253238

This leads to the issue that these Comments are not synced to my instance https://lemmy.rimkus.it. Is it a known issue? Can I do anything to get Response Comments to Comments Synced to my instance?

Thanks in advance Jonny