More armor breaks = less damage?

Tipo

Act 6.3.4 first fight on the spectre path vs ghost using Corvus glaive a single armor break medium attack does 3020 damage and 5 armor breaks is doing 2653 damage. How or more importantly why is this happening?

Cliffordcan

Some bug with physical resistance. I don’t know the details, just that it’s been around since he has been released