As shown in the lower left part of the bottom status bar, you have one or more circular references.
When Excel detects a CR, it aborts the recalculation cycle. That can cause inconsistencies in cell values.
Re: All cells from CY8--CY15 are set to "Accounting", so no cell is set to "text"
First, it appears that CY8 is not formatted as Accounting, based on the far-right-aligned position of 500 in the image.
Second, having a numeric cell format does not prevent the cell value from being interpreted as text, for any of many reasons. You need to use ISNUMBER or ISTEXT to be sure.
That said, the fact that the status bar Sum includes the value of CY8 is probably sufficient to confirm that CY8 is indeed numeric.
Finally, in the future, it is also important to check (and inform us of) the calculation status, namely Manual v. Automatic.