I see you're an Athena player, can you test this out for me if you haven't already done so?
Are you sure that he does the first f+B off the ground and not with a manual hyperhop?
I was trying with the "off the ground" variation for the first f+B, and with a manual hyper hop for the second, but when I get the second f+B (in the air) to hit, my EX Phoenix arrow hits, but not fully, the second part whiffs, making it impossible to continue the combo