I had about 6 cards in my last review show up as correct and have gone from level 6 to level 7 (So they turned red), however I did not review those cards and then when I went to manage deck and looked the cards up, they were still marked as level 6.
I doubt this matters, but one of the words was 面接 in the 10k Kitsun Japanese deck.
Heya!
Am I correct in assuming you mean they showed up on the results page after your review session?
These might be leftovers from a previous session (incomplete reviews), or from when a layout was filtered and the review is then supposed to be done (e.g. 2 out of 3 layouts are done, but you filter out the 3rd layout in the deck settings → 2 out of 2 are now done).
The weird thing is that they never actually ranked up 
The results are saved in your cookies and are only locally, so they have to have been in either this or the previous session. Perhaps invisibly due to the filtering mentioned above?
I definitely don’t remember seeing them in a previous session. They did show up in the next review session though and then did level up after I reviewed them so everything is working fine minus it just showing up.
I don’t really pay attention to the results page but they stood out because they were red. No big deal, just thought I’d bring attention to it.
Gotcha, please do let me know if something similar happens again though! I’d like to check what’s going on.
It happened again. I screenshotted it for proof 
The screen shot is a little messy but… the top part is results of the test. I put my clock in there so you had time stamp. Searched the card in the deck showing its a level lower, and I would bet anything its in the upcoming review at 12pm. I did not review that card and did not have any novice reviews in the session I just finished.
Going to take a look!
I figured out why! My fault. I do both sentence and vocab decks. It came from a sentence card and not a vocab card.