a copy of workbook show data missing alert from tooltip while from original workbook it doesn't . Though tooltips and data related stuff are not tempered by me. What could be the reason for this?

I created a copy (Y) of workbook(X), 

All i did in Y was some formatting to borders and logos.

after publishing Y to server, i am getting alerts from multiple sheets with "Data Missing" as field from tooltips.

After comparing both workbooks, found that the tooltips are same in both.

In original file also, the 'Data Missing Field' message was there in tooltip preview but was not shown in tooltip while hovering over data points; Whereas in my copy, the message was there while hovering over the data points.

What could be the reason for this, as i didn't tempered with any dimension/measure from tooltip.

Can't recreate the workbook due to data privacy.

Want to know in detail.