sfplay~ does have problems playing some 4 tracks .WAV, that’s the reason why this topic started (I attached one that works in QT, DP, Audacity but not with Max).
I continued to check the bytes of .wav files. It seems to me that sfplay~ plays correctly .WAV files created with a WAVEFORMATEX structure (i.e. wFormatTag = 00 01) but not those with a WAVEFORMATEXTENSIBLE structure (i.e. wFormatTag = FF FE).