It could be a spawn, beacon refresh. when i go back to the top of my acrobatics farm ihave to wait 3 second for beacon to refresh and graceful is 100%, the first 3 or 4 drops can be *lagged* kinda and doesnt do Graceful fall. Hope that helps, if not Iron is a noob lol mooooooooo
Graceful Roll is an active skill; it is activated by sneaking (Shift key by default) while falling. It is only effective if the sneaking is started 20 blocks or fewer before impact. Every level, the chance for a successful Graceful Roll is increased by 0.2%, with a cap of 100% at level 500. It can negate up to 14 damage points, or 7 hearts."
it needs to be about 15 to 17 then move if you are with in a close area it will hit a max xp in that area. i changed mine to 30 or something and it stopped working so im going back to 15.
I think this is yr issue