Sprint music stops shifting songs when the phone is locked

[ck4huns]

I've checked the earlier posts and found no similar complains. Before I upgraded the ROM from 6.1 to 6.5 (both are original), Sprint Music plays only when the backlight is on. On pressing the power button to lock the phone, music stops. But now, the music continues while the phone is locked, to the end of that ONE now playing song. Then u hear the clock-ticking, sounds like the music is lagged at the start point. Light the screen and press play button to go on.
OH, shiiiiiiiiiiiiii....