I think my 2012 Zero S ZF9 has the motor problem described by others in recent posts.
Late last fall (soon after I had the firmware updated to fix the original "glitch") and again this spring (I didn't ride over the winter), I often had brief incidents (always on the highway, and usually at the same speed) when the motor would stutter, grind, and slow the bike a few mph. It was always brief, and I could usually get out of it by rolling off the throttle or accelerating. Then it was fine the rest of the ride. It always seemed to hit at around the same speed (around 60 mph at first), so I figured I just had to avoid going that speed. But then it started happening at other speeds (such as 65 mph), still at highway speeds. But nothing I couldn't handle.
Last Thursday, though, things got worse. It happened an extra time in the morning when I was accelerating while passing a car. On my evening ride home from work, it started happening at slower speeds than ever before, around 45-55 mph, and it didn't go away when I changed speed. And it wasn't brief. It lasted at least a minute or two. I was worried I'd have to pull off to the side of the road and wouldn't make it home. It was OK for most of the rest of the ride, but came back again near the end of the ride (again, on the highway).
These recent rides were all in Sport mode, so on Friday, I decided to go for a test ride in Eco mode, and it was even worse. It started much sooner into the ride, and at much lower speeds (around 25-30 mph). And this was much more of a stutter, and it really felt like I had no power. I stopped, turned the bike off and on again, but the reboot didn't help. I had the greatest trouble when I tried to go up a hill (again at 25 mph). I had a car behind me at that point, and I had to pull over because I was worried the car was going to run into me, because the bike felt like it was stalling.
I emailed Zero about it Thursday evening, and someone responded Friday evening saying that I need to take it to a dealer to get it diagnosed. The nearest dealer willing to service it is over an hour's drive away, and I don't feel comfortable riding the bike down there with it behaving this way, so I'm probably going to have to have it picked up and delivered.
Summer is just beginning, and now I'm worried (from past experiences I've been reading on this board) that I'm going to be without a bike until the fall, and I'm going to be out a big chunk of change to have the motor replaced. (My warranty is expired.) What's worse is that I still owe a few thousand dollars on the bike and am still paying it off.
For the past two and a half years I have been a huge advocate for Zero, singing the bike's praises to everyone who'd listen. (I even had a coworker buy one recently.) But this has me quite disappointed, and really bummed out.