Chasing the knocking noise after brake in...

[ADEN]

I am having bad luck getting my m20 to work properly.
I finished rebuilding my m20 :
New sleeves.
New bearings rod and main.
New valve stem seals.
New valve guides.
New rings.

Other stuff were within specs as per my mechanic i started it fine and do 50km braking in and then the drama starts with knocking noise at 2k my mechanic said it is my camshaft i got a clean complete head noise still there, I googled and i suspect a spun bearing popped the oil pan and all rod bearings are fine then i found this after guessing from where it came i looked up and found my #1 piston is missing this piece couldn't take a pic but i highlighted from a google picture .....

Why the pin housing got cracked like this???

[ADEN]

After pulling the head and got the piston out it i found out that the piston wrisrt pin got out although the circlip still installed and badly scored the new sleeved cylinder bore
Stupid mechanic.

[digger]

How did wrist pin shift if circlips are in place?

[ADEN]

How did wrist pin shift if circlips are in place?

I managed to get the pin out and in while the clip installed maybe the mechanic shouldn't have reused it or at least test it before putting it in.

I have read the same thing had happened to hondas and gms guys.

Maybe i'm just having a bad luck