Survival timer stopping

[(PSN)kukui_fox]

I've been trying to complete the nightwave weekly mission to spend 30 minutes or longer in a survival mission. I've managed to do so twice, but both times the timer has stopped at 29:59. I receive the 6th 5-minute reward, but not the nightwave reward. 

Including instances where the rest of the team has left before hitting the 30 minute mark I've probably spend in excess of 3 hours trying to get this quest reward. It's a bit of a long mission to keep attempting to check if it's working so am unsure what to do. 

Edited July 29, 2019 by (PS4)kukui_fox
Initial post wasn't well written