Index Array Formula Assistance
 

Are there limitations to the Index array formula? I use this formula on a
price sheet that is about 13,000 rows. From about 11,000 to the end and a
small patch toward the beginning, the formula will not copy down to the
cells. I have tried dragging it down and also copying the formula, pasting
it in, and changing the cell references. Sometimes it will change back to
the orginial cell references and then disappear. Is this happening because
of a limitation to the formula or is there something wrong in the formatting
of the individual cells? I would appreciate any help anyone can give me.
Thank you so much in advance.