Failure of average function to calculate correctly

I have a spreadsheet in which I have one column of figures, with a second column giving a running average overn7 days, using the average function. I drag the cell with the average formula down on a daily basis to give a new 7 day average. This has worked perfectly. However, it has started returning zero when dragging down. I have made no change to the formula or formatting. The formula has the correct cell references in. I am at a loss as to why this is happening. Any ideas?

The version of Libre office is The OS is Windows 10. The file type it is saved as is .ods

This is a test spreadsheet showing the problem.

Test 1.ods (13.0 KB)

Thanks for your help.

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Upload a document with the average formula and the referenced cells.

Don’t turn off Data → Calculate → AutoCalculate.

And after having it turned on again hit Shift+Ctrl+F9 once to recalculate everything.