Sorry late reply! The stupid Steam forum does not notify me when new post comes! :C
Hmm, hard to say really, not a common problem. If you have other track mods, try disabling them, and if that does not work, try to disable grass altogether. Any changes?

I have a similar issue, though it crashes my game straight to desktop upon completing certain tracks, or with the Dune tracks, upon loading into the track my car and the entire field fall through the map for infinity.

The last one is reported to be releated by having more mods affecting surfaces in the game. Try moving the TVTP mod to the top of modlist. If not other mods files will load and be prioritised before TVTP which might cause a range of issues.
Then there are the cases of random crashes, which is hard to pinpoint sadly ;/ Don't have any sort of debugging tools available, meaning it is a lot of trial and errors.

引用自 The Very End：

The last one is reported to be releated by having more mods affecting surfaces in the game. Try moving the TVTP mod to the top of modlist. If not other mods files will load and be prioritised before TVTP which might cause a range of issues.
Then there are the cases of random crashes, which is hard to pinpoint sadly ;/ Don't have any sort of debugging tools available, meaning it is a lot of trial and errors.

Thank you for the reply. Doing other testing so I'll move things around and get back to you with results.

Disabling all tracks and moving it to the top worked as expected, however moving to the very end (hah hah) with all other tracks enabled restored the lost tracks. Yay!

Glad to hear it sorted itself out! Think it works with other mods too, just got to make sure it is on top :)