Almost looks like bad Metallurgy. Improper heat treatment etc. (bad batch)

I'm sure it's happened before, but doesn't get reported in detail like OP.

Thanks for the picture guys. My 230k KM 09 7AT sprung a coolant leak at the weep hole. When we open the oil sump we saw the same shape of metal and that lead me to this thread. We opened the valve cover and discover almost all the retainer on the intake side were broken and i guess lucky enough that none of the valve dropped. Changing to a used retainer from donor engine soon. Gallery gasket were perfect so really not sure what trigger the retainer failure.

I have the same problem and same broken bits found in my oil pan.

2009 Nissan 370Z Nismo with 30,000 miles

No engine noise and no engine problems.

I only found this because I decided to upgrade my oil pan and found the same exact metal bits in the same exact broken seed shape as the forum picture