I fixed it, the error was in the library code: https://github.com/ariiiman/skylake/blob/master/src/Animation/Morph.js

where the getArrfunction(t) is located there is an implicit coercion that threats the string as a number:

S.Morph.prototype = {
      .............
      .............
      getArr: function(t) {
        for (var i = t.split(" "), e = [], s = 0; s < i.length; s++)
          for (var n = i[s].split(","), r = 0; r < n.length; r++) e.push(+n[r]); //this one causes the error
        return e
      },
      isLetter: function(t) {
        return "M" === t || "L" === t || "C" === t || "Z" === t
      },
      ...............
    }

so e.push(+n[r]) becomes e.push(n[r]). In javascript it is possible to make the string a number, if possible (only with the characters 0-9 in the string). If that isn’t possible, the result is NaN… In my case it tried to push a concatenation (with(+)) and expected an array (with method split()) of number but found a string that’s why I got the error: Error: <path> attribute d: Expected moveto path command ('M' or 'm'), "NaN NaN NaN NaN …".

Works well now!