Two Tanks and Mission Glitch

I found Tank when I got hopelessly lost trying to find a hunting ground to sweat creatures. I talked to him and got a mission to hunt 10 pappoo, and I completed the quest quite easily. I did notice that there was another Tank levitating at 2nd floor height a little ways from the building. After I accepted the mission, neither Tank will talk to me. I need to complete the mission so I can move on to the next part, but I can't speak with him anymore. Any help? Thank you!

 

My apologies, duplicate thread. Request thread close!