The error is incorrect word order after 'so many times.' When a sentence begins with 'so + adverb/adjective' for emphasis, subject-auxiliary inversion is required. Instead of 'So many times I have,' it should be 'So many times have I.' This formal construction places emphasis on the frequency and is grammatically required in this structure. The same pattern applies to phrases like 'So difficult was the test that...' where inversion is mandatory.