Enduring Impact + Cranial Impact + Resonance only gives 1 frenzy charge?

Maybe I'm doing something wrong or misunderstanding something, but I only get 1 frenzy charge when I heavy stun a unique boss while I have Enduring Impact support on the stunning skill and Cranial Impact in the passive tree. I should expect 4 frenzy charges, if I'm understanding the interaction correctly.

Hmm... I think you might be right.
In my brief testing, when I have Cranial Impact allocated, I also only get 1 Endurance Charge when it is used alongside Enduring Impact.

When I unallocated Cranial Impact, I get 3 Endurance Charges.

It seems like Cranial Impact might be overriding Enduring Impact in some way. I hope this can get spotted and fixed soon!