So what I am saying is if the program spool (drum) is improperly formatted then the error will be a constant, meaning if read by a reader it will be reproduced as an error carried forward.
The key punch machine by its self was prone to errors also. These were related to internal switch failures which would conspire to punch nothing at all, punch the wrong character, or punch no character at all.
Finally the reader had the same error pretext meaning that the error could be at the reader and the reader only- at the point in plant where the Body plate was being read and then the data transmitted to the Graphotype where the Graphotype then punches the plate with an error.
So what do we have?
Like almost everything else simple human error. or failure to properly maintain the system. (Again root cause is human error)
Drum programming at the key punch (human Error)
Defective switch at the key punch (Maintenance Problem)
Key Punch error (human Error)
Read error at the graphotype key card reader (Maintenance Problem)
The consensus is that an incorrectly coded "bad programming drum" is the most likely cause of these batch anomalies.
Ken Shirriff is a wealth of knowledge on these machines the following describes the problems and complexity of how these machines worked along with the various modes of failure.
http://www.righto.com/2017/12/repair...-keypunch.html