Empowering Circuit effect not stacking

[ANFortney]

I'm not sure if it is supposed to stack because the power does not specify, but the icon on the buff bar does stack. I have attached a screenshot demonstrating.  I am a MM but I had a friend check on his DEF and it seems like it it the same there.

[Rudra]

City of Data says Empowering Circuit replaces its existing effect when from the same caster and that only the highest value applies.

https://cod.uberguy.net/html/power.html?power=mastermind_buff.shock_therapy.empowering_circuit&at=mastermind