When the report is rendered on the screen in preview mode, it looks okay. However, when it is saved to PDF and/or printed, table borders might have slightly different thickness depending on relative location on the sheet. I believe this issue is related to DPI scaling.

Anyway, there is a solution. At least, if you are not after any fancy behavior. To create solid border of the same thickness:

1. Assign BorderStyle to Solid.
2. Put BorderWidth as 0.5pt.