certain things cause it to send gibberish to the serial terminal

[baconwaifu]

files returns gibberish for the filenames, even 8.3 short filenames
and sometimes the thing just starts spitting out gibberish to the terminal, try loading a file from SD card to see what I mean (just imagine seeing HHHHHHH repeating indefinitely until you hit the reset button on the card)

[AndreNeedham]

The gibberish is because the function to output a string was changed to assume the string was in PROGMEM (program memory) but the filename strings coming off the SD card aren't PROGMEM. I fixed the issue for myself by making a version of printmsgNoNL that just outputs a string normally instead of doing pgm_read_byte. Something like:

void printFileNameNoNL(const unsigned char *msg)
{
while( *msg != 0 ) {
outchar( *msg );
msg++;
};
}

Then change the one line (2118?) in cmd_Files from:
printmsgNoNL( (const unsigned char *)entry.name() );
to:
printFileNameNoNL( (const unsigned char *)entry.name() );

I didn't see any other instance where a string was being printed that wasn't from PROGMEM.