But if the slow lasts through the turn and therefore can be negated during the turn, then you could use reckless to remove the slow.
Now, there is nothing in the book that says a model cannot be given fast (from different sources)only once in a turn. Its simply that it's not worth doing as they don't stack so every (+1)ap after the first is ignored. The important thing here is that the slow and fast cancel out and the rulebook specifically says they are both removed. So the slow lasts into the activation either till the end of the activation OR up until the point the fast cancels it out
SO, the question I have is; when the second fast affects the model, why is it ignored? The first has been removed so the ap is not stacking. I can see no other reason why it should not apply.
Just to be clear we are only talking about situations where a fast is applied to cancel out a slow and then a different ability or effect gives fast.