Strange problems using SD Card and VS1003B based board

The problem might not be that the wires that you are connecting are floating. I am suggesting that one of the "legs" of the IC that controls the VS1003B is not traced to ground = is floating. This is because sometimes breakout manufacturers are lazy/careless.

I had a similar problem once with a FTDI chip on a cheap Nano clone = I had to put a jumper connection from the tiny IC leg to ground to force it low.

I suggest you check the datasheet of VS1003B, see what pins are supposed to be pulled low/high. Test if pins are connected to ground / high or not.