If something is broken in this area, it is either as a result of a mighty shock (impact), fatigue (tiredness) or material fault.
I think you should try and establish a cause, and then take it from there.
I would tend to not trust something that has broken! but I would feel much better if I could establish what has happened.
I can't comment about the inlet exhaust cams, but to my great surprise I realized that they are identical on the 1.8 turbo, although positioned slightly differently determined by a little pin on each cam sprocket. The two different part numbers, however, indicate that this is not the case for the V6.
I would do a proper repair, or none at all. These are difficult engines, requiring lots of effort. Either do it right (and by that I don not necessarily mean by the book!!) or buy a Toyota
I only belatedly read the part of the christmas pudding!! I would start my search there. I have a sneaky feeling this may somehow have a relation to what you see. Is it on the oil side or in the water?