Leaflet only allows polygon layer from GeoJSON to be displayed one time

I have used an AJAX call to load a Black Sea GeoJSON that I want to display as a polygon on the map.

var blackSea = [];
var blackSeaData = new L.GeoJSON.AJAX("./blacksea.json");
blackSea.push(blackSeaData);

blackSea[0].addTo(map);

The first time I use blackSea[0].addTo(map) it works, the polygon is displayed, and I can even change its style, but if I clear the map with clearMap() and try it again it does not display. If I clearMap() before the initial call it still displays, but after I clearMap() again it does not.

What could be the problem here?

edit: the clearMap() function:

    function clearMap() {
    for(i in map._layers) {
        if(map._layers[i]._path != undefined) {
            try {
                map.removeLayer(map._layers[i]);
            }
            catch(e) {
                console.log("problem with " + e + map._layers[i]);
            }
        }
    }
}