TIFF generated with JAI won't fax

Question

I have tried to generate some simple black/white TIFF files with JAI, which I have then sent to a fax via a tool on an IBM AS/400. The TIFF files look fine on my computer, and the faxing tool also sends them without problems, but the result when the fax machine prints them is just some random pixels in the top of the page.
I have tried all the fax compatible encodings - COMPRESSION_GROUP3_1D, COMPRESSION_GROUP3_2D and COMPRESSION_GROUP4, with the same result.
The funny thing is, that if I open one of the generated TIFFs in IrfanView and save it again with the same encoding, the fax machine is able to print it perfectly. So there must be some settings that are changed, which also can be seen by inspecting it with a tool I found called AsTiffTagViewer.
My original file:
ImageWidth (1 Long): 300
ImageLength (1 Long): 300
BitsPerSample (1 Short): 1
Compression (1 Short): Group 3 Fax (aka CCITT FAX3)
Photometric (1 Short): MinIsBlack
FillOrder (1 Short): Msb2Lsb
StripOffsets (38 Long): 450, 490, 530, 570, 610, 650, 690, 730, 770,...
SamplesPerPixel (1 Short): 1
RowsPerStrip (1 Long): 8
StripByteCounts (38 Long): 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40,...
Group3Options (1 Long): 1
After being through IrfanView:
ImageWidth (1 Short): 300
ImageLength (1 Short): 300
BitsPerSample (1 Short): 1
Compression (1 Short): Group 3 Fax (aka CCITT FAX3)
Photometric (1 Short): MinIsWhite
FillOrder (1 Short): Msb2Lsb
StripOffsets (1 Long): 8
Orientation (1 Short): TopLeft
SamplesPerPixel (1 Short): 1
RowsPerStrip (1 Short): 300
StripByteCounts (1 Long): 1101
XResolution (1 Rational): 0
YResolution (1 Rational): 0
PlanarConfig (1 Short): Contig
ResolutionUnit (1 Short): Inch
Software (10 ASCII): IrfanView
So the question is, whether someone knows which of the tags that are relevant for making it fax-able, as well as how to set them with JAI, which I haven't figured out yet.
My code:
//Read PNG file, save as TIFF
String sourceFile = "jaitest.png";
PlanarImage image = JAI.create("fileload", sourceFile);
BufferedImage bi = image.getAsBufferedImage();
OutputStream os = new FileOutputStream("jaitest.tif");
TIFFEncodeParam param = new TIFFEncodeParam();
param.setCompression(TIFFEncodeParam.COMPRESSION_GROUP3_2D);
ImageEncoder enc = ImageCodec.createImageEncoder("TIFF", os, param);
enc.encode(bi);
os.close();

Answer 1

Problem solved by experimenting. Don't ask me why, but it works when I do this:
param.setWriteTiled(false);
param.setTileSize(IMG_WIDTH, IMG_HEIGHT);