Just got my 2018 Bolt back from the Chevy dealer warranty repair where they fixed the same clicking sound by replacing the SL-N-Cylinder (04650-C) and its fluid. They also replaced the brake booster control module assembly. My service advisor said the parts would have been over $1200 + labor. He also said the tech found the issue in this forum and not on the Chevy service bulletin website. Thanks to everyone who gave answers to this issue. The dealer also said that Bolt/Volt forums are more active then all of the other Chevy forums.