With some riven mods if the "random" Stalker or any Syndactes come into the tileset when you are trying to open these mods, it interfeers with or nulifies some of the riven challenges. I was on the last wave of a defence mission to open up a riven mod that did not allow any damage to the cryopod. The stalker appeared on a teammember and delt damage to the cryopod, causing me to fail the challenge and have to repete it. This needs to be addressed. The game has been pushed to a higher livel for the players who ran through the missions then whined that they were too easy. But to have the game written so that a boss can interfear with the riven challenge, this is actually going too far and needs to be fixed.