At this stage I have someone going to Japan at the end of the month who will find a half cut for me, this way I can fix the engine and box in one go. Then I will pull the box apart to find out what went wrong as my particular issue does not show up anywhere on the internet, But would like to know if the reverse idler gear is somehow misaligned or missing teeth. So hopefully by babying the car I can get through the next 2 months before doing the swap.