no, you see it wrong.
you say:
flag goes down, and at a certain point it stops. when the attackers are gone it suddenly goes down this much that attackers still win.
==> unfair win because of bug
this is what it is:
flag goes completely down and at a certain point, it reaches the bottom (attackers should win now), but the round doesnt end. seemingly the flag isnt down yet, but in fact the attackers have already won. the flag wouldnt go further down without the bug. at a certain moment, the server registers that the flag is down and declares that the attackers have won
==> delayed, but fair win
Its very easy to see when the flag is bugged, you have too look how high the flag is above the base of the flag.
however, i dont think it would be bad if it would be removed.