Apparently copying and pasting worksheets into one workbook may have gotten us into "a bit of a pickle." Each worksheet that was and pasted into a workbook contained the same cube (SSAS) data source. Each subsequent paste after the first one simply incremented the data source number, not recognizing the previous four sheets were using the same data source.
As one might imagine this workbook is a dog, from a performance standpoint. I thought, "No problem! I'll just do a 'Replace Data Source' and consolidate my extraneous data sources into one!" Not so fast, I encountered the dreaded "..encountered an unknown error." dialog.
Is this a know issue? Is there a workaround beside revisiting all 40 worksheets and rebuilding each one with the same data source? No, I didn't do it to myself, but I do have to fix it. Thank you in advance for any ideas you may propose.