I repeat it again and again and I do not know, how else I able describe it. Plink has the mechanical origin. It occurs naturally in all strings, on any guitar, any bass, any piano... Sometimes more, sometimes less - there are many factors which affect it. But very essence is determined by physical laws. For most musical instruments this is not a problem. But piezo pickup is very sensitive to this type of vibration. In fact, the "plink" occur not only on the E6 string but also on A5 string. At the A5 string is it removed in eletronica. The same should happen also on the E6 string, but here it just does not work - ERROR. Some guitars have due to a mechanical reasons only hushed plink on the E6 - these do not have a problem. Otherwise, there is nothing that could save similarly, as it works well on the A5 string.