I did a check by decoding all SMIME mails to readable text with openssl- sure, all bad emails had 0x00 as the least signicant byte.
Then i looked at asn1 spec and discovered it was a bit vague about if the least significant byte had to be there if it was 0x00.
I inserted a line into the custom written IBM 4764 CCA driver written in c called by JNI.
Then all emails decrypted.
The team dropped their jaws- they had been figthing with it for 1 year and I diagnosed the bug only by looking at the good/bad ratio :)
I might remember some details wrong- but the big picture is correct :)
I think the singular power of an experienced programmer is being able to reason about high-level structure, while being able to deep-dive into any lower level detail, anywhere in the overall system, and therefore be able to carve out large swaths of problem space just by /thinking/. That's much faster than typing-and-executing-and-reading-logs.