1. Based on evidences most of the descriptions he gave in his documents were inaccurate, there were discrepancies in these;for example of the rulers accounts he gave before and after life time, and the geographical details he gave.
2.It was not possible for him to embark such a long journey(73,000miles) at that time he quoted in his narration,due to the circumstances of the events then; the means of transportation was not fast then
3.Because many expedition had occurred before his time,there was believe that his narration was based on compilation of contemporary travel reports (Plagiarism)of the period. E.g most of the pilgrimage accounts he gave were word-for-word of Ahmad Ibn Jubayl.