Link to video

https://www.dropbox.com/s/mde6u4pgk6y4omn/Video%2012-08-2020%2C%207%2020%2059%20pm.mov?dl=0 

Hi.

That could be many things, from minor adjustment to more important fix needed, and assuming the 4 CD adjustment knobs are adjusted right.

Can you pay close attention to what seem to scratch, for example by removing all the discs and testing each position.
If the noise stops its maybe just the clamper height adjustment which is easy if you're a little handy.

Let's start with this for now.

matador,
I have removed the CD's, and the grinding & scraping noise has stopped !

I selected CD 2 position and it moved to that normally.
I selected CD 3 position  and it moved to that normally.
I selected CD 4 position, it moved to it, but missed it a little.
I selected CD 5 position, it moved to it, stopped with a LOUD BANG, and immediately shut down.

When parked in CD1  position, I selected CD 6 position,
it moved perfectly down towards CD 6,
but when it reached CD 5 position, it stopped with a LOUD BANG, and immediately shut down.

I cannot see what it hits when it stops.

Ok,

Then It "may" be just the clamper. But something seems to happen around position 5.

Have a look at the clamper, from the side of the unit. It must be parallel to the glass and the main alu panel. Not pointing downward, nor upward.

Then try to watch, from the the open side of the glass if the loud bang comme from the surface or from the "deep" inside of the unit.

Inspect the unit for sign of torsion or something misplaced around that position.

The clamper is parallel to the glass and aluminium face. Aprox 4mm away from the aluminium.
The sound comes from deep. It hits VERY hard, and can be felt in the cabinet it sits on.

I have found what it is hitting on !!
On the left hand track that the clamper slides down, at CD 6 position,  there is a loose piece of plastic in the track.
As the clamper slides down, it hits this piece.
This piece is loose, i can move it with the ruler in photo 2

I have posted photos here
https://www.dropbox.com/s/5l5rc91pxfsgg0p/01.jpg?dl=0 
https://www.dropbox.com/s/pjc24htxiiqks7y/02.jpg?dl=0 

This piece also fell out of the box when i unpacked it. 
I assume it is related ??? https://www.dropbox.com/s/olgvl92dq9lpdsz/tab.jpg

Can't see where the tab come from.

As for the piece stucked in the middle of the rail, there is a plastic cover in the middle of the unit on the rails, on the side close to the commands.

Check it is still in place. If it don't you can try to carefully remove it and put it back in place. Maybe the tab also come from that part and explain the fact it dont stay in place. Mine as that part lost and it dont prevent the unit to work and is also totally invisible from the outside.

You are right !! 
My cover is not there !

Now i have to work out how to pull it apart, to remove the loose cover 😂