While researching to get Checkpoint times from Ghosts in Replays (yet unsuccessful unless you race against one in a gamemode), I think that Maniascript takes the checkpoint times there from CTmRaceResultNod::Checkpoints (https://next.openplanet.dev/Game/CTmRaceResultNod)
However, for Openplanet, Checkpoints in an UnknownType, and apparently its a "strided array" which is not supported yet.
While researching to get Checkpoint times from Ghosts in Replays (yet unsuccessful unless you race against one in a gamemode), I think that Maniascript takes the checkpoint times there from CTmRaceResultNod::Checkpoints (https://next.openplanet.dev/Game/CTmRaceResultNod) However, for Openplanet, Checkpoints in an UnknownType, and apparently its a "strided array" which is not supported yet.