Hello Vicky,
I04 status signifies 'BDOC stored before update task' , and before the Bdoc goes into final status(SUCCESS or ERROR) it goes through multiple Intermediate states(signified by I01-I02 etc.)
I04 is a similar state of Bdoc wherein Bdoc fails to get confverted to a final state becasue the update task had failed. This is the reason you're getting this error repeatedly. It is the calling Application which is at fault here(combined with any user exits etc. that might have been introduced).
btw did you try report Z_PROCESS_BDOCS_I04(from note 835761)? If this report fails, it means there were no corresponding inbound Bdocs found for these I04 Bdocs. That'll answer your second question.
BR,
Rohit