Issue when using the copy down, its displaying information from the row above

I dont know what setting I have toggled, so I am struggling to turn it off.

When I key in a formula in a cell, it returns the correct value, then I click the fill down button and I expect to see the same formula applied, but this time on the next row down an so on. The formula in the background looks good, but the data is coming through incorrectly.

I have recorded my issue here - https://i.imgur.com/6UXyBOJ.gif


Any ideas on what I have done to cause this (Excel 2016)?

In Formulas|Calculation|Calculation Options, choose Automatic.