I've been noticing what certainly must be a bug.
Example scenario:
>Hunter with Knock-em-Down and Ember of Torches aspect
>Proximity knife kill shielded-wizard
>Knife isn't refunded
It works everytime on regular mobs when not yet Radiant, but not on solar shielded enemies, it's up to chance. Seems like with shields, the burst kill is being processed before Radiant is applied to you.
But even when Radiant, there's the rare chance it won't count.
This also happens with Titan solar grenade with Ashen Wake equipped, the grenade won't refresh sometimes if there was a solar-shield enemy in the group of enemies that were destroyed by the bomb, as I guess the shield-burst damage sometimes takes priority, denying you the kill count. And this doesn't even deal with any Radiant stuff.
-
Since the shield burst damage is what usually kills the enemy, it won’t count as a throwing knife kill and therefore won’t refund it. What I recommend is just removing the shield with your weapon then dealing the final blow with the knife to get it back. For ashen wake, the trait only says grenade kills, not multi kills with a grenade, so it should work if you use it in a group of enemies with a solar shielded one. For the shielded enemy however it should be the same situation with the knife.