Probably the beatmaps don't have a correct offset. A local offset feature (per-beatmap offset) has already been requested on this thread.
gintoki147 wrote:I don't know if this is a known issue, but still...
Even though I adjusted the music offset in the options menu, some songs are clearly out of sync with the objects, while others play just fine.
Maybe opsu! is not reading the beatmaps' offset correctly?
I'm playing on Android btw