I don’t know if this is a bug, but it seems like it to me. I completed this mission without buying out the whole inventory.
Do the chips not count because they aren’t bought with gold? It seems like they should count. Think you could check this out when you and the team get back, @Polaris?
Is it possible that you had completed the challenge already and just not noticed? Or did you literally check it immediately before buying most of the store items?
I was keeping track of how many times I bought out the market. I noticed that the red dot telling me I completed the daily quest for progressing in a challenge appeared before I bought the chips.
Perhaps your guild perks made it above 6 slots, and it only counts six slots?
Just read 
Ok, well that seems weird. You’d think buying out the market means buying out the market.
That’s what I would have assumed too, but I suppose that would have been unfair on anyone who’s in a guild that has unlocked additional slots. This way seems counter intuitive but at least it’s the same for all players.
If I had known that sooner I would have saved myself from spending 37 diamonds lol
