SSRS ERROR: Index was outside the bounds of the array

Hi everybody!

I have some reports designed by SSRS that have similar design structure contains a table which it’s first columns show some information, and next columns contains a subreport that get a parameter from first columns and shows related data. at first reports works fine, after some times when user click on Export to PDF, face to following error:

Index was outside the bounds of the array

I think It happens because the subreport data exceeds from one page, while I place it in a textbox.

When Iset repeat table header row on each page to false or set the table direction LTR (changed from RTL) the error gone away.

Thanks in advanced to help me find thereason (at first) and solution!