var space = "\u00a0";

Note that songs is a global array.
When your function is called the first time, it modifies the array. (parses and replaces the playback times)

The second time your function is called, you get the error, because you are trying to parse the playbacks again even though they are already integers.

You either need to modify the array once (outside the function).
Or create a new array with the parsed values if you want to do this every time the function is called.