When do you get the error trapper? Is it before you can build the other one? If so, your ride might be corrupted (error trapper every time you click on it).
Your initial problem is odd, though. Because it's not a hack where you'd get an odd corruption. You just changed the lift speed to 9mph? I guess check to see if the launch speed is something other then zero (like 2 or 4). Otherwise, I'm not really sure what to tell you.
Now I imagine most people don't do this but you may want to start:
If you're doing a park with a lot of hacking (or even a little) save it as multiple save files. Pick something like every day or whenever you get a lot of work done and save a new file. Like MyPark1 and then MyPark2, MyPark3, etc.
Like I'm only about 1/4 of the way through my new realistic park (of which a secret screen is hidden in my profile...), but I'm already on save file 22- mainly because I've lost a ton of work due to corruption.
It's just helpful because if your game screws something over, you just revert back to the previous number and keep on building. Always look around to see what's up before you save the game. Just in case.