Don't look at the AvQ. you can have a full 6* team, but these have internal programming, with limits, of contribution, positive-negative impact in players that are next to, +/- impact in defensive labours or appearing in attack.

If you can add a screen capture with the page of the team stats, this that have the info' of goals assistances and MoM, then I can maybe suggest you something.

Basically always is the same, when a 6* team looses is because the manager put all attention in the stars, and do not test players or discard, and you have to take into account that you can have 2 exact players, and if are exact ST's one can score 40 goals in a season with 5* and the other 3 with 8*.

there are min/max. of effectiveness, agressivity, etc insid the internal programming of every player.

Add the capture if you can to take a look at the team contribution per player.