My China 1.8" Slim MP4 player can't play song after charging it.. help me.

I just bought 32GB China 1.8” Slim MP4 player ipod 4th clone on ebay for USD 20.50. I put on it at about 5700 song and 200 videos, working well before charging. After charging at full bar using wall socket at 4 hour long, several video and song folder are corrupted and auto reboot when I click into song folder. So, I formatted the mp4 and download the song again. It working nice, but the same problem occurs every time after I charging it. What going on? Can anyone help me.
Thank you very much.

p/s: My sister’s china Mp4 player 2.8” touch screen 32GB working well without any problem, even after falling down from double Decker.