When using Magnar III, cast both arcane armor and arcane weapon. Only arcane armor shows up in enchantment slots. The card shows both enchantments active, but only arcane armor shows up in enchantment slots.
Also, when Magnar looses battle, the arcane armor enchantment is still there, but card no longer says he has arcane weapon. When I recast arcane weapon, card once again indicates enchantment.