I've never come across this myself, your report must be gigantic!
I would get in touch with support to get a speedier response to this specific query. To get around it, you could try adding a new custom property, and split the report up. For instance, if you set up a new node custom property called 'Report Group' you could assign a value of 'A' to the first group, 'B' to the second, and so on.
You would then simply edit your report, but add in the additional logic to loon for nodes where 'Report_Group' is equal to 'A'. To duplicate the report, you simply copy it, then change the logic to look for 'Report_Group' 'B', and so on.
Wouldn't take as long as you'd think to do it this way