After the ‘Secrets of the Machine God’ update - an erroneous notification that a new penance reward can be claimed by speaking with Hestia appears on the upper right - even if there is none.
The message goes away after going into the penances tab (and seeing there is no change) but comes back upon entering back into the Morningstar, either from choosing another operative, leaving/entering the game, entering and coming back from missions, and the Psykhanium.
Happened to me before Secret of the Machine god update as well and I made a bug report of it, but was going to post a new one today as I have now completed every penance and it still show the message.
It was slow until the new map maybe got 0-15 kills on other maps, so I went to the new map on lower difficulty and got between 30-80 kills per run depending if my teammates slaughtered the mobs before I could get them to barrels or not.
Dang sounds like a good strat, you also have quite a bit of patience to have done that, I envy you. I usually can’t deal with achievements such as that, in fact I still am of the opinion that it’s completely ridiculous as a penance. I probably will end up forcing the more annoying ones on lower difficulties besides the barrel one, like the Grimoires since I never pick any up and I always say “No.” ingame when somebody pings one lol.
