File.Seek called by AudioSource.PlayDelayed takes too long to run if it built as APK.

Hello, we are currently developing mobile game with Unity 2018.4.36f1.
Since we found vulnerability in global-metadata, we've encrypted metadata. After encryption, nothing was wrong with AAB build but it makes problem in APK build - it is too slow to play game.

By profiling, we figure out that File.seek() takes long time (about 0.1sec), and find this function call was from AudioSource.PlayDelayed(). Does anyone suffer from similar problem with APK build or solved this kind of problem?