If you enter a formula in a cell, e.g. =MIN(IF((B14:B15) > 0, 3, 50)) and forget to use <ctrl><shift><enter> to make it an array formula, you cannot fix it by editing the cell and typing <ctrl><shift><enter> You must edit the text and change it in some manner before clicking <ctrl><shift><enter>. I.e. click to put the cursor somewhere, delete a character, reenter the character you deleted, then type <ctrl><shift><enter>
Or simply add a space at the end.
*** This bug has been marked as a duplicate of bug 38014 ***