I posted the post below on AK120 thread and I opened a new thread since I'm sick of tired of the basic bug of this supposedly high end players:
"guys, i had the same problem with this 120 to my 100, but this time its worst. I loaded some songs freshly ripped. First to the sd card ,a lot of the songs would play for like 10 seconds then an error came on "Your songs is not supported format, play next song ? Yes/No". I had the same problems with 100 but taking the memory card out and reinserted it then manual scan it usually solve the problems although later on it came back again. But the same procedure will solve it again. Its a pain in the neck though.
Now with the 120, the same procedure wont solve it. Then i moved the songs to internal storage and the same things keeps happening again. Firmware is the latest one. It's very disappointing for 1k-ish DAP if they couldn't solve a basic problems like this.
Any ideas for troubleshooting this problem ? Thanks"
Latest update : factory reset/relocating the files to internal storage/rolling back the firmware as far as version 1.3, all didn't help.