[SOLVED] MPD Error failed to decode flac ._ file

[Nutul]

It sounds like you have hidden files created by MacOS.

The solution is to delete all the hidden files.

great suggestion, unfortunately I could not find any extra files with ls-la

They may be in another folder, or in the root of the USB disk, or somewhere there; if you read the post pointed by @the_bertrum you may find some more information. The pattern, and the symptoms are exactly those.