in the end we found out that the most likely cause of the 2 broken clutches was that the "mechanic" had only fitted one dowel pin (instead of the 2 toyota has put in) between the engine block and gearbox.
This most likely caused a misalignment between the crank and input shaft that the clutch plate had to try to deal with ... and didnt ...

IF you want something done right then do it yourself scenario ....