Our set of TBS1052C oscilloscopes exhibit a strange effect when multiplying two waveforms. The attached shows the multiplication of two sine waves (yellow and blue waveforms) with equal frequency, 2:1 amplitude and a small phase difference. The first screenshot (Waveform1.png) shows the expected result from multiplication (red waveform) - a 2x frequency sinewave with DC offset. However, when changing the volts/per division of one channel, the second multiplied waveform becomes distorted (Waveform1.png). We have tried different oscilloscopes of the same model and they all exhibit the same problem. However, interestingly the version B doesn't have the problem.