Random Item Sold?

[SpikeJKD]

I just played a match were I was in base purchasing Juggernaut. I had more than enough souls to just purchase the item outright (something like 6900) and when I purchased Juggernaut, one of my other items - Stalker - just sold itself. I had plenty of inventory space, it didn't ask me if I wasn't to sell an item to purchase Juggernaut but it just... sold Stalker and I don't know why. They seemed to happen in the exact same second.