simpler than the spider and more probable.....
Before the scaremonger lot chime in just check its not something like a lost bra wire trapped under the tub or something that might not cause the noise when the drums rotating one way but does the other way.
Piece of wire, a coin, plastic, all can float around in water and make very little noise but when the tub drains and empties and a certain tub speed can cause the foreign object to move from its usual hiding place and cause a noise.
Take the top off the machine and shine a torch into the drum while rotating it should enable you to see anything that is causing the issue first.
You might have to stick your head inside the drum to see clearly. - much easier than stripping it down.