I'm answering my own question. Sorry to bother you all. I'm not a professional for electronics or electrical items but have limited experience in repairing such items. After opening primary speaker box and investigating wiring on its electronic board, I found that the wire connector having 5 pins (USB +, USB -, Aux +, Aux -, Aux G) had loose/pulled out Aux Ground pin. Moreover, there was an Aux out connector on the board that disturbed sound when touched. I suspected its metal base was touching other lanes on board and I fixed it by raising a bit. And thankfully, problem resolved! Perhaps one of these or both were the reasons that Aux was missing sound and giving noises specially on separate adapter. However Bluetooth was giving clear...