You're formula is returning this array
{"71";"15";"54";"45";"57";"77";"78";"85";"50";"08";"81";"10";"08";"8"}
As you can see the final digit is repeated on it's own. Try
=MAX(FREQUENCY(0+MID(A2,ROW(INDIRECT("1:"&LEN(A2)-1)),2),0+MID(A2,ROW(INDIRECT("1:"&LEN(A2)-1)),2)))>=3