I see previous topics from years ago regarding copy paste from excel but they all appear to be resolved. I am having the same issue again, 2p19, both on your demo pages and my site.
Copy/paste From Demo to Demo WORKING
Copy/paste From Demo to excel WORKING
Copy/paste From Excel to Demo BROKEN
*select multiple cells in excel, ctrl c, select one cell in Demo results in data from 6 cells copied to the 1 cell only
*select multiple cells in excel, ctrl c, select same number of cells in Demo results in data from 6 cells copied to each of the 6 cells. Each of the 6 is filled with the exact same thing (the data from all 6 excel sheets)
Using chrome browser and excel. Google sheets functions the same as excel.