... If an error occurred, the very last output of emchain will be something like emchain: BEWARE: One or more of the tasks ended in error ! You should then look into the log file for a specific message like emchain: BEWARE: That task ended in error ! ... If the error occurred in the last exposure, the intermediate files will not be erased, you may also inspect them (if they were erased, rerun emchain for the particular instrument and exposure where the error occurred, setting stoponerror =Y). ...