Forge Version: 14.23.5.2847
Mod Version: 1.10.23
This was tested with a clean installation of Forge, AS and Baubles with no other mods to make sure it wasn't caused by incompatibilities or by changed configurations from a modpack.

At first I suspected it was caused by a high increase in Perk Effectiveness, but it was working as expected even when it was higher than +100% so I then tried with the only perks that affect enchantments

when Amulet Enchantments is lower than +50% Consistent Luck still works as expected, giving the unenchanted pickaxe Fortune I

but after increasing it past +50% the fortune level bugs out

and it also appears to be lowering the level of existing fortune enchants when wielding the pickaxe

This bug persists after reconnecting or restarting the game, and even after resetting your perks and taking Consistent Luck again without the increased amulet effectiveness perks.

derp