here are some shots and a sample from the 1st time i had the problem. it was actually the left channel this time, as opposed to the right one i was having problems with most recently. there are a couple where teh channel doesn't actually drop out on the waveform but it sounds as if it pretty much does completely.
this was STS9 at Wakarusa mod460/ck61 > v2 > 722 using different cables