no its not a bug your missing the safehouse halloween event. You can cheese it pretty easily if u cover the area in fully upgraded tripmines, remember that the headless dozers cant see u if you look at the floor and when you need to kill them after you've run out of tripmines shoot where you think the head should be with a suppressed thanatos

After All DLC/mission already done one down, i didn't got them mark. is that bug or missing one?

P.S: My friend's host with all mission DLC completed..

This guide is for one down heists not overkill...

Actually, I dont think you have to do the DLC ones, as I accidentally unlocked one of the difficulty masks whilst never even doing heists like Golden Grin, or The Bomb: Forest, or Birth of Sky

is this guide still relevant?

-_-

Overkill just wants us to spend more money on DLC so we can get the cool looking masks

yes you do have to complete the dlc ones
if you dont have the dlc you can join a game but make sure its not in progress otherwise you will not get the credit

Do I have to do all the DLC?