fo:table border

To output the table cell border I use
  <fo:table-cell border-width="0.1mm" boder-style="solid">
for all table cells.
Since table cell borders overlap, some border is thicker than others.

Why is that only few cell borders are thicker than others? Is there any
reason for this. Has someone come across with this? How could I show table
cell border with uniform thickness?

Regards,
Satish

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