2001 Lexus RX 300 Timing Belt

Recently I took my Rx 300 to a local mechanic who replaced the timing belt pullys water pump and spark plugs. 3 months 18,000 miles later car starts missing hesitating and shuts off in the road. I take the car back to my mechanic who originally replaced the timing belt and he stated the engine had alot of top end damage and I would need a new engine and stated was better off just to scrap the car. I looked into a remanufactured enginge my mechanic stated it was too big of a job for him to handle. So the car went to another shop and this shop stated that the timing belt was not installed to manufactures specification and this is what caused the engine to fail. His explanation was When the crankshaft is TDC (Top Dead Center). The left bank camshaft was 4 teeth off, the right bank camshaft was 3 teeth off. This made the engine in advance position before Top Dead Center. The camshaft sensor was trying to retard this engine via computer control but to far out. Because the timing was so far out this engine failed. He took pictures documenting everything. Original mechanic is saying that is impossible car must have jumped timing that it would have never run like that

Not sure what to belive here can you please help shed some light on this.

Thanks