Hi,
For what its worth, I have the same issue described by the OP but I'm on FS20
Works fine on x2 but on x4 wings starts uncontrollably left and right to 30 ° of bank each side as op said.
It does not matter what flight, it does the same on each flight i'm using 4x.
Im not using fsrealistic, I do use fsuipc.
I've also seen someone mentioning this in one of the youtuber A330 Driver videos as well
PS: I don't have this issue on 787 nor 777 (both using 4x to perform LH)
Please address this