I guess your HB needs more balance, or you need to respec into surefooted to prevent it.
Elusive HBs like to do these wiggle moves to fake out/slow down pursuing defenders.
https://glb2.warriorgeneral.com/game/replay/830977/951696You can see toward the end that surefooted fires twice cause the HB is doing mini jukes that hurt balance.
I'm guessing Black Noir starts to do one, fails the balance check, and then falls down. The rain doesn't help.