One way to find out for sure is to mark the prop, near the hub, and the hub itself where the two marks are next to each other. Then go for a ride, and afterwards, if the marks moved, then your spun. If not, probably something else.
Usually its just plain spun.Might make it to 3000 and when it slips it won't stop till you slow.Sound kindof like a carb issue starving a little for fuel as it slows fuel catches up.Or maybe some wierd rev limiter failure.