HI Manasa,
Its very difficult to replicate, but check below
1] Check if any enhancement is implemented which is causing this
2] Create new customer , new vehicle master and check if the issue occurs again.
3] Raise the issue to SAP and if require they will issue new SAP note to fix this bug
4] If none of the things works our implement enhancement before pricing is carried out to check and populate correct region.
Regards
Ganesh