Ages ago I noticed (so did others) that certain Chaos Arcade tasks didn’t complete even if done multiple times. For example, if a task to reach 100mph is given but the car is already doing over 100mph it cannot be completed even if slowing down and accelerating. Same for reverse speeds. I think if a car is stationary for a “remain stationary” task then speeding up and stopping doesn’t count.
While I’m here it’s still stupid that there are “ultimate wreckage” and even worse “wrecking ball” tasks in these arcades; it’s very rare that they’re possible within the time limit.