Hi. I have a spreadsheet where I enter numbers in columns E to I.

I have some simple sums that are calculated in columns J and K. Cell J5's
formula is for example SUM(E5:G5). Cell K5's formula is for example
SUM(E5:I5).

So here is the really strange issue: as I enter data into cells E5, F5, G5,
H5, I5 (in that order), my formula in cell J5 changes magically to SUM(E5:I5)
-- with no warning whatsoever. What the heck is going on??