Let´s stick to my first gif for a second.
It´s important to keep in mind, that we can rule out 1st wave debris objects to be the gash-maker.
One can easily confuse that from different angles...
Also this scene gives some good indications what exactly to look for in other footage.
So let me highlight what I believe we should look for:
Watch the gif some more times and keep looking for these objects.
They seem to move just as one object at one point, but then they seperate from each other.
There is one smaller thing highlighted in red which seems to be breaking of or something and then diverging from the rest which is highlighted in green. (I think the smaller object could be a deformed floor section, carried/pushed all the way by our actual gash-maker, highlighted in green.)
So please look at the gif some more times to get a feeling for the highlighted objects, when they do appear and how they behave:
Alrighty then...
Let´s have a different angle:
You see it don´t you? That toppling core column that almost seems to go for WTC7?
Well, this one is NOT the actual gash-maker, it doesn´t even hit WTC7.
However, the actual gash-maker can also be seen, looking like a bunch of crap falling synchronously in the foreground of what really looks like a tall toppling core column here.
In the following picture, what I highlighted in orange would be the "obvious" core column that in fact is NOT the gash-maker, while the actual gash-maker is hidden in the green area (which should be the same green area from the other picture more or less):
to be continued...