When I apply the rear brakes and rock the bike forwards and backwards the rear hub moves slightly with the bike. I changed the rear bearings 6 months ago but not the cassette bearings.
There is definitely no movement on the suspension links and no side to side movement of the back wheel.
Can anyone please help me:(

Can you wiggle the wheel in the drop outs? What frame and axle is it?

Do you have floating discs? If so the rivets on the disc will have some play.

Check obvious things first.
Is it movement of the pads in the caplier? Or a bit of play in floating rotors (if you use them?)

Do you have floating discs? If so the rivets on the disc will have some play.

Most likely this^^^

^^^^^^ Agreed, play at the rivets

Play in rivets, or maybe even loose disk bolts, or pads rocking slightly in the caliper?

I have the same issue, no floating discs on my bike. Noticed it a couple of weeks ago, been ok so far…
Still, I’d like to know what it is.

Thanks for your replies, it’s my floating rota.
Is it dangerous??