I used to get bug reports for FLAC caused by this very same problem.
FLAC has a verify mode when encoding which, in parallel, decodes the encoded output and compares it against the original input to make sure they're identical. Every once in a while I'd get a report that there were verification failures, implying FLAC had a bug.
If it were actually a FLAC bug, the error would be repeatable* (same error in the same place) because the algorithm is deterministic, but upon rerunning the exact same command the users would get no error, or (rarely) an error in a different place. Then they'd run some other hardware checker and find the real problem.
Turns out FLAC encoding is also a nice little hardware stressor.
(* Pedants: yes, there could be some pseudo-random memory corruption, etc but that never turned out to be the case. PS I love valgrind.)