The RTF rendering automatically switches to the Tables rendering mode whenever a Crosstab/Table/List is detected in a report. This rendering mode throws an exception whenever the report contains PictureBox with one of the following sizing options.
The RTF export should work with all PictureBox sizing options regardless of the rendering mode.
To work around the issue currently, one can either force the rendering engine to use the Frames rendering mode using the RenderingMode device information property or set the Sizing property of all picture boxes in the report to AutoSize.