Increase the line-height of the select by a few pixels.

This worked for me.

Changed this:

select {
    line-height: 15px;
}

To:

select {
    line-height: 17px !important;
}

It happens because of the padding. Consider only using padding left and right, combined with min-height.

You could increase the height of the select item:

select{
   height: 40px;
}