Not from the clues given, sorry. If the motor is not able to turn over and you have metal on the drain plug since this july I would expect something has broken or come loose inside and you are simply rolling the dice on which cover to pull first.
Given the issues these have had with similar issues on two machines on here I would start with the rear cover. understand if nothing there you next have the choice to remove the top end (piston and cylinder) in the frame or just pull the motor. Maybe attempt removing the front cover first.
I had time to work on the traxter today. I decided to remove the engine completely to facilitate work and space.
Once the engine is out I turn the engine manually and it is a "clock" style noise. It turns on one side and stop(block) leave on the other side again the noise and stop(block).
Do you still advise me to start towards the back cover?
so hard to tell but from what I see nothing is terrible so far. Check that all the bolts holding the rotor are tight and you will start digging deeper looking for the source of the steel that is stuck to your magnets. In my case the metal was contained in the rear cover area so for it to be built up in that area there is a good chance it originated from there.
I would pull the flywheel next to check your starter clutch as they can produce metal when failed. Flywheel nut is reverse thread iirc, verify this and then you can easily impact it off.
I found the problem. Behind the rear cover everything seems in very good condition. I removed the head from the motor, because the noise seemed to come from the piston. So here it is just to look at the pictures to understand the problem...
So the piston was hitting the head and broke the piston now the question is what was allowing the piston to hit the head. It looks like you have the piston off the rod does the rod or crankshaft have up and down play? The cracked piston would not be the source of the steel you have found on the magnets but a bad main being could be.
You need to solve the riddle of what allowed the piston to hit the head as well as where the metal came from . Bad main bearings or rod bearing couple be possible so they need to be checked. You may need to buy or make the special 46 or 48mm socket to remove the nut on the front to split the cases. I did not need to so stopped at that point but there were a couple of them for sale on ebay for about $130usd.