Maokai sapling did not cancel back

I saw a sapling failling to cancel a back twice today, once, the sapling lande about 1.2 second befor the completion of the back annimation, and did not get the time to triger and explode, so i did not gave it too much thought, but the second time, it was halfway throught the annimation, it got to triger and explode, buthis damage did not cancel the back which completed about 2 sec later.