I have some experience and everything tested to get perfect loops with all loop-able audio formats
- Android: ogg, flac, wav &
- iOS: ALAC, IM4A.
Between ogg and wav formats, I had found no differences in the looping. However, the looping on some Chinese devices (Xiaomi, OnePlus, …) with the TaifunPlayer no longer works. This also applies to the wav (PMC) format.
Post your “perfectly looped” ogg sound here, I’ll check it.
PS: On iOS (Xcode, Swift 4) I never had problems with the looping.