I think it’s likely some video codec thing.

nostr:npub1gcxzte5zlkncx26j68ez60fzkvtkm9e0vrwdcvsjakxf9mu9qewqlfnj5z I dont know much about video codecs - could there be some video encoding used on android side that is not yet supported on iOS?

https://github.com/damus-io/damus/issues/3035#issuecomment-3090770079