If Lazio succeeds in taking advantage of Bayern Munich instability in the second leg, of course Lazio will create an unexpected surprise. But I see that Bayern Munich have managed to get through their difficult times in the Bundesliga where they have returned to winning ways. For the second leg, Bayern Munich are still very much favored because they are playing at home and also in terms of strength they are still very favorites to beat Lazio.
Not yet back to winning ways smoothly. Bayern Munich is still having several problems, so winning their last match in the Bundesliga against RB Leipzig was not easy even at the Allianz Arena because Kane needed more than 90 minutes to score Bayern Munich's winning goal at that time.
Playing at the Allianz Arena in the second leg, I believe Bayern Munich will finish well so that the title competition will be even more exciting if Bayern Munich qualify.
Before facing Lazio, we need to observe Bayern Munich's game against Freiburg first. That's where we can assess whether it is true, as you say, that Bayern Munich has really returned to winning ways convincingly.