Fishman Power Tap Earth

The price of this pick up is higher than other famous brand eg: K&K, LR Baggs. First i buy this as the reason of this pickup can collect the percussive sound good.after i install and use it around 30mins,one of the pick up volume suddenly drop down.i think maybe is the original battery ran out so that i brought a new battery .After that same problem happen within 3 days.i told this to the guitar shop and the repair guy said is the hardware problem not related to the install process.I return this product and request for refund / replace a new product.Thomann don't accept and just arrange me a new repair service .after waiting for half month i received it.the letter from thomann said that they test it 20min and notthing happen so they just sent this back for me.ARE YOU GUYS BLIND?i describe the problem detaily and wait for a long time.This is the final result what i got.such a terrible shit drama.