Try this array formula with remove duplicates on Shift Column.
In E4, array formula copy across and down :
=IFERROR(INDEX(A$1:A$956,SMALL(IF(($C$1:$C$956=$E$3)*MATCH($A$1:$A$956&$B$1:$B$956&$C$1:$C$956,$A$1:$A$956&$B$1:$B$956&$C$1:$C$956,)=ROW($A$1:$A$956),ROW($A$1:$A$956)),ROWS($1:1))),"")
p.s. array formula to be confirmed by pressing SHIFT+CTRL+ENTER 3 keystrokes together
Regards
Bosco