the speaker won't need replacing or fixing, if it does it will only happen again if listening at the same volume with the same audio files, if its only intermittently its the track itself (due to compression of audio files when recorded or converted into mp3 or lower quality formats) each recording will be slightly different that's why its only happening sometimes, its always going to struggle with really low bass from the size of the speaker (normally an 8" or over is best for strong bass) and its capabilities especially over Bluetooth , it will only handle a limited frequency range and will struggle at the bottom end especially if on a louder volume, try lowering the bass or volume that may stop it.