I can not re-create the problem on the demo site. I conducted more tests on our site. The problem is not consistent. I can export some reports with a chart and a table with no errors. On the reports with the error - if I remove the table the report exports with no error.
More information. The following MDX Will always create an error on a PDF export. If I change the filter to a value other than HW the export will work with no errors. This query will return a table with a single value with a single row and column.
Select non empty HIERARCHIZE(DISTINCT({NonEmptyCrossjoin(AddCalculatedMembers({ {[Service Date].[Serv Yr Mth].DefaultMember}}))})) on rows, non empty { [Measures].[Mbr Mths]} on columns From [Cost] Where ([LOB].[LOB Xpress].&[HW])
Please open the report in the design mode. Click on MDX toolbar button and XML button. Copy the XML into a text file and email the file to support@reportPortal.com.