QMX thumping issues on CW

Running firmware 1.00.017, here is how the QMX sounds on CW 20-80m. The only change to settings I've made are to make the sidetone volume relative to AF gain (not absolute, as is the default). The thumping that you hear remains the same at all power levels, from 2 watts out to 6 watts out and is roughly the same with headphones as with the powered speaker used here.