Problem with 1D mark III

Hi,

Last week I bought 1D mark III second hand.
And I see it some problems.

When I shoot with shutter speed more than 1/1000 some line he appears on picture.
But when I shoot under 1/200 is nothing wrong.
In my opinion is or shutter or mirror.
Please help me IF YOU KNOW something about this issues.
I attach some examples.
Thank you.