Repro steps:
1. Open QA attached project "repro"
2. Open scene "0"
3. Enter Play Mode
4. Wait for Cube to hit the Terrain

Expected: Cube lands on the terrain and the scene goes on
Actual: Editor crashes

Reproducible with: 2017.1.4p2, 2017.2.3p1, 2017.4.6f1, 2018.1.5f1, 2018.2.0b9, 2018.3.0a2

Notes:
- Crash doesn't occur when the terrain is created in the Editor
- Crash doesn't occur when Cube doesn't have a child GameObject only errors are thrown and the GameObject disappears
- Crash doesn't occur when Transform's scale is the same as BoxCollider's Size

Crash:
0x00000001423FDC28 (Unity) physx::shdfnd::sort<physx::PxsContactPatch * __ptr64,physx::SortBoundsPredicateManifold,physx::shdfnd::ReflectionAllocator<physx::PxsContactPatch * __ptr64> >
0x0000000142402976 (Unity) physx::PxsContactReduction<6>::reduceContacts
0x0000000142402099 (Unity) physx::PxsSolverConstraintPostProcessTask::mergeContacts
0x0000000142403D7A (Unity) physx::PxsSolverConstraintPostProcessTask::runInternal
0x00000001423B4762 (Unity) physx::Cm::BaseTask::run
0x0000000140B30657 (Unity) PhysxJobFunc
0x000000014087FC4E (Unity) JobQueue::Exec
0x000000014087FF6E (Unity) JobQueue::ExecuteJobFromHighPriorityStack
0x00000001408803E9 (Unity) JobQueue::ProcessJobs
0x0000000140881E29 (Unity) JobQueue::WorkLoop
0x0000000140A71DB8 (Unity) Thread::RunThreadWrapper
0x00007FFDF7F93034 (KERNEL32) BaseThreadInitThunk
0x00007FFDF8E61431 (ntdll) RtlUserThreadStart

Fixed in: 2018.3.0a2
Backported to: 2017.4.15f1, 2018.2.8f1