
We heard similar issue volume of m4a tracks varies from other several customers.
It seems that the issue occurs after recent Window 11 update.
According to the other customer, the issue also happens with Windows Media Player.
So we suppose the m4a decode library contained in the recent Windows 11 update has some problem.
We expect the issue will be fixed in subsequent Windows update.
But if the issue only occurs with certain m4a tracks, the issue may be improved by re-encoding m4a (make m4a file again) with iTunes or some other tools.