Our washing machine, tumbles, but after a dozen turns, pauses then tumbles the opposite way!

Cleaned the trap at the base of the machine - it was surprisingly not clogged or dirty.
Tried to turn the drum inside the machine, this moves quite easily, and when turning this quickly there seems to be a lite 'clicking' sound as the drum comes to a stop.
feet are equally balanced on the floor, as they have been for the past 4 years since we moved here.

Am hoping I can fix this myself or at the very least it not be an expensive repair!

Any ideas what is happening with this?

Thanks