My translation into English is 'Or could be a mistake in the head build process' - i.e. someone's cocked up when building up the cylinder head (installing the valves, guides, seals and valve drivetrain), so it's not oil tight and oil is getting into the combustion chambers. An assembly error, basically. Unlikely to be the issue unless the engine's recently been rebuilt.
My translation into English is 'Or could be a mistake in the head build process' - i.e. someone's cocked up when building up the cylinder head (installing the valves, guides, seals and valve drivetrain), so it's not oil tight and oil is getting into the combustion chambers. An assembly error, basically. Unlikely to be the issue unless the engine's recently been rebuilt.