Spell Thief's Edge not working with Morgana's W

When I play Morganna support with the Thunderlord's Decree mastery and a Spell Theif's Edge against another support with Bond of Stone, the Spell Thief Edge's gold bonus is sometimes not activated when Morgana's W is used. I've noticed that this does not happen often and only occurs with the Spell Thief's Edge. This has happened in at least 3 games. I believe the bug is occurring because the game is having trouble tracking the damage happening to the adc and the enemy support when Bond of Stone is in play. As a result of this bug, I'd apply my W spell but not have any bonus gold even when the damage is registered.

I may have misinterpreted the cause of this bug, but the underlying problem is that sometimes when I cast my W as Morgana with Spell Thief's Edge, the bonus gold is not delivered even when damage is incurred by the enemy champion. The stacks of my Spell Thief's Edge are also not affected even when damage is dealt.