I have done a multi bom inquiry on 84677.
Through the levels of the bom 524693, 524840, 524833 to 524834 and 524699, 524840, 524833 to 524834
This means 524834 appears 2 in the BOM for 84677 as dated 1/7/15.
Can you check my working, so 84677 should use 63 of 524834 twice = 126, not 63 as you have stated.
So back flush would seem correct.
Please check my working and advise.