got an daily rating of F without any reason

[fragball]

i played a mission when the time for the rating was due, and after i send my mission crew back to the vault i saw the this rating was F instead of my usually A-
the happyness of course was still at 92% (like it is nearly all the time. i left no incidence when i switched to the mission, and also there was (and are) no dweller with any radiation damage whatsoever...
only reason i can see for this crap is that in the mission i had to fought against a lot of enemies that gave rad-damage to the mission team and i let it accumulate it a bit to get the most out of my rad-aways - maybe thats why i got the ♥♥♥♥♥♥ rating? before sending the team home, i removed any radiation and healed them of course, but if the timer for the daily rating hitted zero when those 3 dwellers had rad-damage, and if away-team DO actually have an inffluece to the vault rating, it would at least explain it (a bit). though, i really doubt that 3 dudes on a mission with a bad happiness could drop the overall happiness from about 120 dwellers in the vault to a F-raiting at all. if that wasn't the source of the problem, it must be a bug.
anyone else had this on occasion?

[TomCat86]

I had that bug too. No reason, just went to 0 happiness for no reason and back up to 97%