If my experience is similar to others, I didn't have the problem but then in the last couple of weeks it started. Oddly, it isn't all the time, for instance never during live tv, but does happen when streaming movies.
I posted earlier in this thread about the issue, and I'm still finding the same type of scenario I described previously applying for me. I don't do live TV, so it's just streaming movies, episodes, and home videos for me. I continue to find that if I'm in a situation that requires transcoding while streaming, the skips continue to pop up - which is the case if I'm connecting on an external network with limited speeds or the file is a format that doesn't natively play. However, streaming on my home network with no transcoding has consistently worked smoothly.
This is just my hypothesis, but because it appears tied to situations where the data may have to break into pieces more often, I'm guessing the skips are tied to either points where those breaks occur, or perhaps even a buildup of where those breaks are (more on that in a couple sentences). If that's the case, then what should be a seamless stream of lots of connected data pieces is glitching because iOS is potentially reading the data of each piece incorrectly. So if it reads the length or position off by a second for a data piece, then that could explain why it skips back a second during the transition from piece to piece. I doubt it's a full second on a single piece of course, that's just an easy illustration. In reality, it would likely be more like tiny fractions of a second for each data piece that then add up into those breaks every so-many pieces. You all are more than welcome to rip this idea apart though, as I'm definitely not a developer myself.
It would be nice if @ebr and @Luke were able to compensate for this issue, but I'm more than willing to give them the benefit of the doubt when it comes to the balance of whether they can logistically and feasibly do something about it. That's especially true since it still appears to be a widespread issue for all kinds of developers and apps that stream video of any type on iOS 11.