Some existing tracks cannot be built in OpenRCT2:
Octivator
Big Corkscrew Coaster
Atomizer
Bumble Bee
Deep Freeze
These tracks seem to be fine when being built in the original game of RCT2.
However, when playing OpenRCT2, there are no previews for the tracks, and the tracks cannot be built properly as well.
I hope that the teams of OpenRCT2 could fix this problem.