Dark Rift rewards question

Hello Guys,
I have a simple question for those who are doing Dark Rift.
Dark Rift has 13 bosses, 10 of them drops boxes which can drop you accessories (or cron stone etc), the last 3 bosses are not dropping any boxes.
Are the drop chance for the Boxes (Box of the Desperate Dead, Box of the Distorted Dead, Box of the Silent Dead, Howling Dead Man’s Chest) 100% rate? I mean do you guys gets a chest every time you kill a one of this 10 bosses? It is really easy to tell for someone who did for example 40 of them.
My case is that I did 10 bosses which should drop a box, but I didin't get any of them.
The standard loot for every 10 bosses today was Dark Spirit's Greed, some of Ancient Spirit Dust and Memory Fragment's, and some Black Stones (Armor/Weapon).
I would be very thankful for the answers.
Have a nice day guys!

 

Did you know RNG thing xD

 

Yea I know, the problem was propably with drop filter, which could be set up to pick only +7 yellow items.
The drop rate for the boxes are 100%.