Normal, no, but I’ve been seeing lots of reports of sync issues with both Lemmy.ml and Lemmy.world. I think both are a bit overloaded and Lemmy.world is still running an older instance of the software too - for now. There definitely seem to be bugs.
I've also programmed a tool to compare two servers and compile an automatic list of comments that are missing, here are examples from recent days: https://lemmy.ml/post/1582415