That's what my synth was doing before I repaired the bad connection I'd mentioned.... it would kick in intermittently with all kinds of 'strange noise' symptoms from the effects, filter etc. Very simply, because that point in question (analog switch connection) was a common control voltage point, it affected all those areas....
Do yourself a favor, please check it out as mentioned earlier before you get caught up in distraction/analysis because the symptoms are seemingly 'complex' for a very very basic issue of an open/intermittent....
You have to remember that these machines are totally dependent on scanning and distributing analog control voltages.... you sabotage that and the whole synth goes out of whack with all kinds of oddities. Otherwise, looking at it with blinders, I would have been faulting the effects unit, the filter unit etc. - again, can't overstate it, that one point was the crux of the whole 'gremlins' issue.