Cracking noise from the pickups (ConcordII)

I just bought a Concord II. What I discovered when playing chords is cracking sound. There is no issue when playing one strin. It is similar to sound of a vinyl record. It doesn't appear in the moment when hitting the strings but I'd say just a bit after.
Does anyone have any idea what it might be? I've already put some spray to pots, but I think it didn't fix the problem.
Any tips much appreciated 

It could be static generated from your fingers on the scratchplate, I've had this on a couple of concord ii guitars. 
My remedy was to line the pickup cavity and back of the plate with adhesive copper foil, creating a "Faraday cage"

Alternatively sand the back of the plate with rough sandpaper.

Sgt. Vimes wrote:It could be static generated from your fingers on the scratchplate, I've had this on a couple of concord ii guitars. 
My remedy was to line the pickup cavity and back of the plate with adhesive copper foil, creating a "Faraday cage"

Should I look for any specific foil (thickness, purpose, quality, etc.)? Or I can just buy any from eBay?

Westbone wrote:Alternatively sand the back of the plate with rough sandpaper.

Thats an idea. So gloss finish is more prone to accumulate static?