Diesel wont start but turns over, camshaft sensor woes?

[Animesis]

It turns over, previous AA check said something with the camshaft sensor. This had been replaced two years prior and it worked. So we swapped it with one from a breakers yard, again, all worked again for a few weeks, now its gone again, bought a new sensor worked temporarily and stopped again!!

Im starting to think maybe the timing chain really has stretched or something rather than than all the swapped sensors failing. Any other sensors that may stop it starting but allows its to turn over? Or anything at all to point me in the right direction?

But I am a complete loss, the car is in Perth, belongs to Taketsugu who's training at the hangar if matey there sees this post!

Any help would be much appreciated as we are both very attached to the car, but if we cant sort this it will have to go sadly...
It has become too unreliable at this point

Thanks in advance