... a slight tweak to this "last" line for the formula in A3:

... INDEX(OFFSET(INDIRECT("'"&$W$2&"'!A:A"),,COLUMN(A1 )-1),
MATCH(SMALL($W:$W,ROW (A1)),$W:$W,0)))

Amended to:
.... INDEX(OFFSET(INDIRECT("'"&$W$2&"'!A:A"),,COLUMN(A1 )-1),
SMALL($W:$W,ROW(A1))))

Amended sample uploaded at the same link:
http://savefile.com/files/6920182
AutoMerge_4_sheets_to_summ_sheet_KeyCol_A_populate d_v2a.zip
--
Max
Singapore
http://savefile.com/projects/236895
xdemechanik
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