Kawasaki Z900 2017 transmission problem?

Hello my fellow bikers

I've bought a Kawasaki Z900 built in 2017. It has only 6700km on it.

I have a problem with the bike when shifting from neutral to first gear.

Every time I shift from neutral to first while standing still the bike makes a loud bang and jerks the bike forward.

I am aware that this is normal to some extent but it worries me that this is a bit too much.

The previous owned told me that he changed the clutch plates on 4000km. It bothers me a bit that the plates were replaced on such a low mileage...

Should re-lubing and cleaning the chain help?

Any advice on what is causing this? Expenses?

Thanks in advance.