I use a wireless lav on my shoots and every once in a while, I will get this distortion sound from the mic. It's like a scratchy, loud, crunchy sound. I've seen it happen when the talent is seemingly standing still and also when they're jumping around excitedly. So I'm not sure that's it rubbing against fabric when it happens. And what do you do with the extra cable from the mic to the transmitter (could that be where the problem is coming from)? Usually, I just bunch it up and throw it in the talent's pocket (no finesse, I know, but I've never seen how to deal with the cable properly). Any thoughts or advice would be great. I hate when I get that perfect take only to have this horrible sound ruin it.
Thanks!

It could be an intermittent loose connection in the cable or connector, it could also be the fact the cable is coiled. Some transmitters use the cable from the mic as their antenna and they're intended to be allowed to hang free. If there's a separate antenna, make sure it is free and clear and oriented vertically.