Weird script behavior. Scaling objects and exporting them as png.

Great! I'm happy to help. The reason that the app.redraw() worked is because you are using the Document.imageCapture() method to do the exporting. It seems that ImageCapture depends closely on the state of the screen updating.

Just for learning, here is an alternative way, using Document.exportForScreens:

(function () {

    var doc = app.activeDocument;

    // keep track of the visible layers
    var visibleLayers = [];
    for (var i = 0; i < doc.layers.length; i++) {
        if (doc.layers[i].visible)
            visibleLayers.push(doc.layers[i]);
    }

    // stop export from creating sub-folders
    app.preferences.setBooleanPreference('plugin/SmartExportUI/CreateFoldersPreference', false);

    var tempLayer = scaleToTempLayer(doc);

    // hide all layers except tempLayer
    setVisibleLayers(doc, [tempLayer]);

    exportAsPNG(Folder.myDocuments, doc);
    // imageCaptureAsPNG(Folder.myDocuments, doc);

    // clean up
    tempLayer.remove();

    // show original visible layers
    setVisibleLayers(doc, visibleLayers);


    function exportAsPNG(path, doc) {

        var fileName = doc.name.replace(/\.[^\.]+/, ".png"),
            file = new File(path + '/' + fileName);

        var options = new ExportForScreensOptionsPNG24();
        options.antiAliasing = AntiAliasingMethod.ARTOPTIMIZED;
        options.scaleType = ExportForScreensScaleType.SCALEBYWIDTH;
        options.scaleTypeValue = 400;
        options.transparency = true;

        var itemToExport = new ExportForScreensItemToExport();
        itemToExport.artboards = '';
        itemToExport.document = true;
        doc.exportForScreens(file, ExportForScreensType.SE_PNG24, options, itemToExport);

    };

    function scaleToTempLayer(doc) {
        var layer = doc.layers.add();
        layer.name = "temp";
        var group = layer.groupItems.add();
        doc.selectObjectsOnActiveArtboard();
        app.redraw();
        var items = doc.selection;
        for (var i = items.length - 1; i >= 0; i--) {
            var tempItem = items[i].duplicate();
            tempItem.move(group, ElementPlacement.PLACEATEND);
        }
        group.resize(200, 200, true, true, true, true, 200);

        return layer;
    };

    // make supplied layers visible, but no other
    function setVisibleLayers(doc, layers) {
        allLayersLoop:
        for (var i = 0; i < doc.layers.length; i++) {
            visibleLayersLoop:
            for (var j = 0; j < layers.length; j++) {
                if (doc.layers[i] === layers[j]) {
                    doc.layers[i].visible = true;
                    continue allLayersLoop;
                }
            }
            doc.layers[i].visible = false;
        }
    };

})();

I added in some extra complications including hiding the layers during the export so we can't see them. But you can see that there is no app.redraw() needed.

- Mark

EDIT 2024-11-16: as per @sttk3's excellent comment, I've added a line that shop stop unwanted sub-folders being created. @Mikolaj35128644esj9 please try this version and see if it fixed your issue.