Lootrun no more gray beacons spawning ? Bug?

I am not getting any more gray beacons to appear. I thought it is strange / unintentional. This is the second time it happend to me. I am rank Grandmaster

Order of what I got rainbow beacon, picked Materialism from the free mission, Right after completing this one I picked up my first gray beacon (boosted with 200% Aqua) and got Orphion's Grace from this one. That I completed in 2 challenges.

after 20 challenges of having 4-6 beacons offered (because i was picking orange beacons) I haven't come across ANY gray beacon.

Is this a bug or are they this rare and i am missing something

EDIT: finished the lootrun with 99 challenges, Didn't find any gray beacons

 

I believe that after 40 missions or so they become exceedingly rare or just straight up stop appearing. So my guess is you just got really unlucky and didnt roll any more greys before challenge 40

 

oh i thought it was after 30

 

probably 30 actually