I've never listened to ska, but this got me intrigued although I think it didn't play that big of a role in this song.

I listened to this a couple of times and it sounds pretty good
To me it sounds like you did certain sections a singer in mind, because I got to say there are- should I say riffs - that you use as a chorus (bar 30-37)

What Im trying to say is they're not repetitive if there is supposed to be vocals, but if not it is repetitive IMO.

Overall the harmonies are nicely done and I find the transitions fluent.
My favorite part is got to be bars 94-106, I know the rhythm isn't super original but it still made me head bob lol.

You should make this song a little longer,
the outro sounds like a build up to a more heavier section..