When Did Torah become corrupted?

[Mohsin]

From what i understand, the revelation revealed to Moses AS became corrupt almost instantly after he died when the Torah got lost. Is this true?
When did it then become corrupt or changed?
Because all the prophets AS that came after Prophet Moses AS all preached what was revealed in the Torah, so why didn't they change the Torah as to what it was originally, removing the corruption and mistranslation and contradictions etc

 

[aljawaad]

HAve neva heard of this. Perhaps u can get your answers from some scholars.