Strange problems using SD Card and VS1003B based board

okay, weird, not find on subject. tried fix whole day, gave me headache

so problem this:

https://www.youtube.com/watch?v=br6xurlujmu

when close cables, plays great. when remove hand, stops  stops when connect other hand ground.

https://www.youtube.com/watch?v=vvamra2pg30

in general, stops processing @ all, not sound. looks interrupts stopped or this.

i'm using info based on http://arduino-cool.blogspot.com.es/2012/10/arduino-mp3-player-i.html have adapted arduino mega 2560, i'm using in project.

i'm attaching schematic i've come to, sorry bad quality, in general, it's same project, i'm using mc14050bp instead of voltage dividers, bring levels 3.3v. that's difference.

these connected pins:

#define mp3_xcs 35
#define mp3_xdcs 39
#define mp3_dreq 37
#define mp3_reset 33
#define sd_sel 31

#define spi_mosi 50
#define spi_miso 51
#define spi_clk  52

i'm using same library agmp3 in thread. i've tried other libraries, result same, it's not in software. tried modifying spi speed values inside project lot of times, without success.

i have no idea what's going on please, me.

wow. weird.
i fixing fathers old radio. had problem touching sound came out. didn't understand going on until dug out datasheet of ancient amp ic. turned out amp ic had 2 operational modes depending on whether 1 of ic pins grounded. when touched radio, pin grounded , sound output speaker circuit. original contact ground had been lost due dried out capacitor.

i have no clue wrong sound breakout, have had problems cheap chinese modules not pins of ic tied ground. fact hand affects sound output suggests me pin or ground controls playback 'floating'. 2c.

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