Static streaks, I think. These happen when you’re loading bulk film too quickly and in low humidity. I don’t really remember when I rolled these, but it was probably in summer and I was probably in a hurry.
If you bulk load, take your time. If this becomes an ongoing issue, I might need to get an anti-static gun. Wouldn’t hurt to use it one some of my vinyl, either.
We don’t have carpeting, so I’m kind of surprised this happened. But it’s something to remember for next time.