It doesn't have to be a full backlash to cause this. Just having a couple loose loops on your reel so that when you cast out you hear the loose loops getting struck by the line coming off the reel will cause a weak spot or even a break in those loops.
The ONLY other thing I can think of is that Shawneramone is sneaking into your garage at night, pulling line off your reels, cutting your line, then reeling in the cut line. He then follows you to your favorite honey hole, hides in the woods and laughs hysterically when you cast off your favorite bait.
If i was a betting man, i wold go with option 2