Gythian's Heart immune to certain melee attacks

Gythian’s Heart’s crystals appear to be immune to certain melee attacks. They don’t show ‘immune’ just no damage occurs. This includes the Fish Slap grenade and the melee portion of the Blade Fury gun. The Facepuncher gun does work.

If you are wondering why your Blade Fury build is eating it on that fight that is probably why.

Ugh.

I was aware that normal melee was not working but I thought it was a collision problem with invisible walls. Really weird that the blade fury don’t go through but facepuncher does.