This is difficult issue. The trade data discrepancies can be explained but need further research. There is an example of reconciliation study between Canada - USA  - Mexico on Compilers Manuals (http://comtrade.un.org/kb/attachments/SeriesF87-GUIDa64a82f464df46f69987ce41855c6cd1.pdf).

For your specific case, in general, country focuses more into Import (due to security, duties, control). Therefore, try to look into import data because generally it has better quality than export.