The problems with transmitting Chinese Medicine over time begin with the reliability of the accuracy of the written and the spoken word. When scribes are used to record a Master's ideas there can be mistakes. As nuances of language and Chinese scrpt changed over the centuries we also run the risk of mis-interpreting what was written.
When we add to this the political landscape that changed the ideology of the time - for example the communists favoring traditional medicine over Western medicine due to a prejudice against anything from the West, or communist ideology requiring the state to provide health care for the masses thus leading to governing bodies being invested in taking cheaper short cuts to make this more affordable, we can see how the written word and acceptable ideology was intentionally changed to suit the current political climate.
We must also guard against the tendency to assume that everything was better in the "Good Old Days" and the sages of antiquity were infallible.