Sorry for the late reply on this old thread, but I have some recent experiences here that may be relevant.
The language of the OP says that on two occasions the the bike refused to go above 75mph. This is a suspicious figure to me, because I know that ECO mode imposes a limit at
75mph [edited: JaimeC, below, is correct - ECO mode imposes a 70mph limit, not 75 - I mis-remembered as I'm rarely in that mode - Jason], and you can define your own in custom mode. When you hit this limit, it's like a hard stop. It just doesn't go faster. What you do to the throttle really doesn't matter (except if you decrease it enough to allow it to slow down), and the throttle response feels normal right up until you hit that magic figure, 75mph. If the OPs choice of words were precise, I'd suspect something goofy happened with the mode the bike was in, or the mode it thought it was in.
Recently, my onboard charger failed (Dec '16). It took about a month to get it to the dealer (thanks to Christmas vacation schedules and such), and during that time my bike sat at ~60% SOC (that was how high it got the night the charger failed.).
When I rode it to the dealer it had decreased to about 56%. It was chilly that day - 40's I think, but bear in mind I ride year-round, 50miles round trip, sometimes in even colder weather (but usually hotter!) I experienced something that has never happened to me on the bike before. The power of the bike kept dropping. At the start of the leisurely 30-35 mile ride, I had to do about three or four miles in interstate. My top speed was fine - maybe I was having a hard time at around 75 or 80, but I really wasn't trying to go faster. (I wanted to take it easy, because it was chilly, and was longish ride to start out a 56%). The rest of the ride was back roads as I wiggled over to Conroe, TX, which I anticipated doing at mostly 50-60mph. Over the course of the trip, though, my top speed got lower and lower, finally limping along with a max speed of ~35mph, with an associated loss of power/acceleration (i.e., I wasn't hitting a limit at 35, it was just running out of oomph.) I think my SOC on arrival was around 20-25%, but I don't have that written down.
Since the charger incident, I've been back in the dealer a few times for follow ups on this, and it still hasn't been resolved, though sometimes it's not so pronounced.
Before this incident, I've had the bike down into the teens, (and even single digits once or twice!) while exploring the limits of the bike, and not seen this kind of behavior. Conversely, last Friday (Apr 14) I got home from my commute with 15%SOC (dramatically lower than normal for my 50mile round trip, which used to land me home at ~35% pretty consistently), and the bike was topping out at 25mph. That was scary. I was having a 'Fred Flintstone' moment, where I had a strong urge to help paddle with my feet! (The least exciting drag race ever: I pulled away from a stop sign, went full throttle, and by the time I got to my street, about 1/8 to 1/4 mile away, I was bumping along at 25mph. Still full throttle.)
Anyway, when this type of powerloss/speed limit is imposed, it feels quite different from the 'governor' type limit. When you crank on the throttle, it just feels like the bike's power output sags. Almost like at a certain point (which moves as it gets progressively worse), increasing the throttle further causes a slight reduction in power, and then further movement has no effect whatsoever.
I'm still collecting logs and data as I discuss this with Zero. They're telling me this is normal, and I'm saying "BS!" I think I have a new battery pack in my near future, or at least a cell replacement or two, because at this rate (I'm currently at 197-- miles, just over two years old), there's no way it's gonna make it to five years/300,000 miles.
Incidentally, at this moment, the bike is sitting at 63%, and my cell balance (per app) is wiggling from 10-12mv. I'll check again when I get home.