Arylic BP50 FLAC bad playing

Hello, in Arylic BP50 some FLAC archives (maybe 1 in 10 each) , who plays well elsewere other players, are bad played in Arylic BP 50. Looks like a timing problem; sometimes plays slower than recorded, and the other times are like “electrical sound” interrupted from the source. It is a problem that always happen in the same tracks, so it must be a firmare flaw. Any tips?