I am trying to print barcode labels for batches of items. My web API can return either a PDF document with all labels, or an array of label images.  I need to be able to print all labels in order from my web application (using BrowserPrint).

First I tried printing the labels as a PDF document and that works for Windows clients running the Windows version of BrowserPrint.  But the same application on android is printing blank labels.
Here is the method I am using:

function zebraPrintPdf(blob) {
    return selected_device.sendFile(
        blob
        , function () { console.log("PDF printed using Zebra BrowserPrint") }
        , function (error) { console.error("Failed to print PDF using Zebra BrowserPrint:" + error) }
    );
}

Again, this works for Windows, but for Android the labels all come out as blank.  I have inspected the payload to the 'write' method that is sent from the browser to BrowserPrint and the PDF is being included.  It even prints the correct number of blank labels (one for each page).  I think this is an issue with the Android BrowserPrint app.  I have an email in to the developers so hopefully they can point me in the right direction.  I'll update if I hear back from them.

Separately, I have tried printing the labels as images using the following ('labels' is an array of Uint8Arrays so it contains multiple images.  Blob type is 'images/bmp' because the images are in bmp format):

function zebraPrintMultipleLabels(labels, blobType) {

    var zebraPrinter = new Zebra.Printer(selected_device);
    var options = {};
    return zebraPrinter.isPrinterReady()
        .then(() => {
            for (const bytes of labels) {
                const blob = new Blob([bytes], { type: blobType });
                setTimeout(function() {
                    zebraPrinter.printImageAsLabel(blob,
                        options,
                        function () {
                            console.log("Image printed using Zebra BrowserPrint");
                        },
                        function (error) {
                            console.error("Failed to print Image using Zebra BrowserPrint:" + error);
                        });
                    }, 500);
                
            }
        }).catch((error) => {
            console.error(error);
            return false;
        });
}

This works (both on Windows and Android), but the labels don't seem to get printed in order, despite the images always being in the correct order. The order isn't even the same when printing the same 10 labels multiple times. Per the documentation, the 'Zebra.Printer.printImageAsLabel is supposed to use a queue to make sure that one command finishes before the next is sent.  But this doesn't seem to be working, even with the 500ms delay from the setTimeout method.

Does anyone have any suggestions or see where I am messing up (with either PDF or printing multiple labels)?