B String "thud" on CR5M w/ Spirocore B

[Gorgula]

I have Pirastro Obligatos on my CR5M which I generally like. Recently, I put on a Spirocore B string to see how it would sound. I like it's tone better than the Obligato B. It's meatier w/ more growl, but not in a bass guitar sense at all.

However, I notice that when I play on the E string, the B string makes quite a "thud" when my right hand fingers come to rest on it. Does this make sense? In other words, after striking a note on the E string, when my right hand finger hits the B string it makes a loud "thud".

The problem goes away if I use the magnetic pickups, but I REALLY prefer the piezos over the magnetic pu's.

I'm thinking it has something to do with the steel core of the Spirocore.

Has anyone experienced this before or have any ideas on how I might solve this problem?

Thanks