I had no problems in my league last year,even though it was the toughtest season for me ,since my quality dropped(NO TOKEN ,BOYCOT)
and cause my league had 3-4 decent and active teams.

Had some problems in some games,but i always have a back up scenario(3-5-2V) And (4-3-2-1).
Haven't noticed problems with the formation,keep it in my opinion .

Try to change some key players..DR-DL-AMR-AML and see what happens.

The problem from the corners u have maybe its a bug, maybe nothing.Try to see what is the quality of ur defenders(DCs) in the head and give them some extra SP in defence.