In fact, the truth about Juventus is that their performances are not stable. They can do well in one match, and in their next match, they can mess up.
I feel like this "inconsistency" applies to many big teams this season. On the other hand, if we're looking at league form I think 4 wins in 5 games is quite consistent. Sadly these forms don't translate well across different competitions. A post-match analysis that I watched suggests that Juventus is struggling defensively at times so conceding 3 goals is not a surprise, even though they managed to keep their GA quite low in the UCL. I agree that the atmosphere of the stadium gives more power to PSV though.