I had almost the same problem on a track I converted from R07, a little difference, the game didn't crash just after crossing the line but when the game switched from the track to the menu.
After a long long long time trying to find out what caused that, I found that it was the name of some of the track's materials that were too long...
Just renaming from "start_building_02_concrete_nospec_material_256_A" (for example) to "Stbuild02_cnm256A" did the job.