Map / Monster Levels Functioning Incorrectly

I'm currently running an irradiated T15 map, and the monster level is 79 (not 80). It also has a boss, and I have the Organised Forces Atlas Skill, so it should be level 80 from that as well. And it's not a visual bug, as items are dropping at lvl 79 and maps T14. Also not the first time this has happened, I just can't figure out why (since it's not 100% repro).

+1