Troubleshooting DeepZoom

My Browser crashes when opening DeepZoom image

One of following red-marked attributes can cause the browser to crash. TileSize has to have expected number. If images have been generated with TileSize=256
and attribute in output.xml is set on 8 then the browser will crash.
Attribute N must be uniquely specified.

<Collection MaxLevel="8" TileSize="8" Format="jpg" NextItemId="16" ServerFormat="Default" xmlns="http://schemas.microsoft.com/deepzoom/2009">

<I Id="9" N="" Source="output_images/Derventa.xml">
   <Size Width="2048" />
   <ViewPort Width="6" X="-3,5" Y="-8,5" />
</I>
. . .

Some Images are not shown

The attribute Height and Width has to be set or not specified. If specified then they have to have values.
Following height means zero.

Some images are shown as Black-Box

The source file (i.e. output.xml) contains more than one image (element ‘I’) with the same identifier ‘N’.

<I Id="9" N="9" Source="output_images/Derventa.xml">
   <Size Width="2048" Height="1360" />
   <ViewPort Width="6" Height="6" X="-3,5" Y="-8,5" />
</I>
<I Id="10" N="10" Source="output_images/Frankfurt.xml">
   <Size Width="2048" Height="1360" />
   <ViewPort Width="6" Height="6" X="-3,5" Y="-9,5" />
</I>
<I Id="11" N="9" Source="output_images/Prag.xml">
   <Size Width="2832" Height="2128" />
   <ViewPort Width="6" Height="6" X="-3,5" Y="-10,5" />
    </I>

Unexpected images shown at specific zoom level