Has anyone had formulas change automatically with no explanation?

I have a user who is using a simple workbook with formulas pulling data
between worksheets, but their formulas will change automatically with no
explanation. They tell me they are not adding or deleting any rows or
columns, just the data.

The only time I personally have experienced anything like that was in a
workbook which had a macro that deleted all rows beyond a certain point
using xlEndUp in the code.
Cutting and pasting could possibly be a factor, or maybe the file has been
corrupted in some way.
Is the user XL knowledgeable? It sounds more like a user error than anything
else to me.
Regards,
Alan.
"DavidA3878" <DavidA3878@discussions.microsoft.com> wrote in message
news:3BCC6FF3-9B21-4F72-9488-5BB0E9E5356E@microsoft.com...
>I have a user who is using a simple workbook with formulas pulling data
> between worksheets, but their formulas will change automatically with no
> explanation. They tell me they are not adding or deleting any rows or
> columns, just the data.