Damaged Sd card. Sd card is damaged. Try reformatting
https://m.youtube.com/watch?v=FqR0BLUH_OI

Hope this is your answer. According to this video the error occurs when you have files on the SD-card that confuses Android OS. The video suggests you format the SD in FAT32 in a PC deleting the files. I suggest a full format (takes substantially more time to complete) as opposed to quick format.