SD card non HC Fat 16 (MS-DOS) strange behavior

Hi,

First of all, I don't really hope to solve this here as I think its pretty much insoluble. But I will give it a shot anyways.

I have Macbook Pro 2015 and a very old stereo in my car. My stereo accepts old SD cards that are non HC type and only in Fat16 MS DOS format. So I formatted the card with my macbook (el capitan) and stereo sees it just fine BUT every mp3 file shows twice on the stereo. And each duplicate is unplayable by my stereo and it crashes all the time. Very frustrating. I tried looking into hidden files but can't see no duplicates in Finder.

Also I have a friend with a windows computer copied few mp3 no problem, no doubles. Very weird.

I am assuming OSX has 2 files in it to make it compatible with MAC and Windows but I can not see it. Well crossing my fingers here and hoping people here might know the answer !!!