How do you know there's a sign of weakness at Bayern Leverkusen? For your information, since the German Bundesliga season is yet to start, we can't really tell if there's a sign of weakness at Bayern Leverkusen, and if you are using the performance of Bayern Leverkusen against Flamengo U20 to say that there's a sign of weakness at Bayern Leverkusen, know that Bayern Leverkusen used their under-19 players to play that match, and you can't use a preseason match to judge a club because a preseason match is just like training that a coach uses to figure out his starting eleven.
Pre-season games are not a true reflection of the strength of a team. Coaches are always experimental during these games which makes them prone to error. Players are tested to enable the coach to know how to use them. Players are also advised to avoid injuries so they might not give their best. It could also be a strategy against opponents in the coming seasons. Clubs might underrate Bayer Leverkusen because of the outcome of the game against Flamengo U20, which could be an advantage. Some clubs won all their preseason games, but they didn't do well in the main season. Let's wait and see what Erik Ten Hag would do with his boys.