Knocking when spinning anticlockwise (& Identify this part!)

Hi all! I'd be grateful for your help...

A couple of weeks ago, I was using my Indesit WIXE127 (UK) (TEV) which I've had for perhaps 9 years from new without any issues.

Just as the wash was finishing its final spin, it began making a loud, rapid knocking sound and what appeared to be smoke came from the machine! Believing the machine to be knackered, I waited for the smoke to clear and had a poke around.

I started by unscrewing and removing the back; there was nothing obvious. Nothing appeared to have caught fire. What I did find however was the plastic part lying loose on the base of the machine.

As I looked through the door, I could see that the seal had somehow become caught between the drum and whatever surrounds the drum (excuse my lack of technical terminology!) wedging the drum and preventing it from spinning. By removing the seal, the drum came free again.

A few months ago, I did use a mould cleaner on the door and there did appear to be some perishing of the seal around where it became trapped by the drum.

So...

My working hypothesis was this:

The seal had perished possibly due to the mould cleaner and part of it had become wedged by the drum. When the drum attempted to spin, the friction caused the rubber seal to smoke. There were signs of charring on the seal.

I replaced the seal today and gave the machine a go.

It's 90% fine in that it washed fine, the drum span and nothing smoked.

What I did hear however was a knocking sound when the drum is turning anticlockwise. It's absolutely fine when turning clockwise. When turning by hand, the same; no noise clockwise but knocking anti-clockwise.

Given the symtpoms described:

1) What could be the issue? My guess is something to do with a bearing or gear? But this an uneducated guess and any ideas would be appreciated...

2) What is the plastic part I found in the base of the washing machine? I have tried to upload pics but for some reason the forum is saying the files are too large even though they're well undersize... I'd describe it as appearing like a small cotton reel around 40mm in length, one end is slightly flanged. It appers to be made out of plastic/nylon with a hole going right through as if a shaft is desiged to pass through it. It's an off white colour.

3) Could this part lying loose be part of the problem?

Many thanks in advance for any guidance any of you kind people can give...

MW