There have been longstanding anecdotes that two of the three ghostly Drain weapons either cannot be charged properly or cannot hold charge properly. I compared all three weapons (000F82FA, 000F82FC, 000F71DD) and their corresponding unique enchantments (0010F22, 0010F23, 0010F24).
The single point of difference between the two "bad" EnchWeaponDraugrMagic enchantments (Axe, Bow) and the "normal" enchantment (Sword):
Axe, Bow have their Effect Duration set at 0 s with Taper Duration 1 s, Full Duration 1 s.
Sword has its Effect Duration set at 1 s with Taper Duration 1 s, Full Duration 2 s.
The mis-setting apparently throws off the "Auto-Calc" for the enchantment:
At 0 s Duration for these enchantments, Auto-Calc Ench. Amount = 23, Ench Cost = 23
At 1 s Duration for these enchantments, Auto-Calc Ench. Amount = 1, Ench Cost = 1 (as currently observed for Sword)
Recommend resetting the Axe and Bow enchantment Duration to 1 s to match the Sword.