ISNUMBER function in an array - not working | Excel forum

I have a workbook where a user enters the area of different crops on one worksheet ("initial data collection") and then, in theory, a second worksheet generates a list of all crops that they have present (i.e. non-zero but numeric vales in the 'area' column). The formula I'm using is:

{=IFERROR(INDEX('Initial data collection sheet'!A$40:A$103,SMALL(
IF('Initial data collection sheet'!B$40:B$103<>"",
IF('Initial data collection sheet'!B$40:B$103<>0,
IF(ISNUMBER(B$40:B$103),
ROW('Initial data collection sheet'!A$40:A$103)-ROW('Initial data collection sheet'!A$40)+1))),
ROWS('Initial data collection sheet'!A$40:'Initial data collection sheet'!A40))),
"NONE")}

where
'Initial data collection sheet' column A is a list of possible crops
'Initial data collection sheet' column B is the column for areas.

The formula worked fine without the 'ISNUMBER' function included but because there are two text headings in the middle of the range, it meant that I was getting the headings listed as well as the crops present, which is no good. With 'ISNUMBER' included, it thinks there are no crops present irrespective of what numbers are in the area column.

Using the formula evaluation tool, I have worked out that this is because the 'ISNUMBER' function delivers a 'FALSE' answer for all cells in my range. NOT(ISTEXT) does give me the crops with a non-zero area, but also gives me the headings (it evaluates 'NOT(ISTEXT)' as 'FALSE' for every cell in the range irrespective of value). I have tried manually changing the format of all the column B cells to numeric as well as using the 'clear all' function on the cells and re-entering every value manually but to no avail.

Please could you explain to me why the ISNUMBER/NOT(ISTEXT) doesn't work, and how I might otherwise remove the two headings from the list of crops present?