Chain skip on new chain. Cassette has only 3200 km on it
I suggest you change your cassette now, before you get accelerated wear on your chain.  At 1% chain stretch, the cassette was as worn as the chain.

Have a very close look at the cassette with your chain in the gear that skips the most.  I suspect that if you add tension by pressing lightly on the pedal by hand, that only one link is making good contact with cassette teeth, and there may even be light visible "under" the chain.  

Of course this is based on rule of thumb.