@lemmy_support Why do only SOME updates reach Lemmy from Mastodon?

I posted to Lemmy from Mastodon: https://lemmy.ml/post/49566110

A Lemmy user's comment on that post reached me on Mastodon. I replied from Mastodon & my reply showed up on Lemmy, as hoped.
https://lemmy.ml/post/49566110/26507040

Later, I tried to reply from Mastodon to other Lemmy comments on the same post. Why didn't these replies reach Lemmy? https://mastodon.social/@modem/_down/116907072443986550