Red flags or not. I don't want an AG that conveniently forgets meeting with Russians. There is no good reason to meet with a representative of a foreign adversary for any reason [alone].
S M I think you're overreacting. AG Sessions obviously did a poor job testifying in front of Congress. If you really wanted to make a stretch, you could call it perjury by the merest of technicalities.
The bar for being charged wirh perjury is quite high, and this falls short. If anything, you would expect the chief attorney for our country to have a better handle on court proceedings than this.
As for meeting with Russian Ambassadors, while its not necessarily a crime, obviously lying about it does raise red flags.