Sounds like an opportunity to give the emulator you're using a touchup! The most common problem is disagreement over the semantics of the shift instructions an

Sounds like an opportunity to give the emulator you're using a touchup! The most common problem is disagreement over the semantics of the shift instructions and how load/store treat the index register "i". In a nutshell, SCHIP on the HP-48 got these wrong, and so modern programs are a mix of depending on VIP-style CHIP-8 semantics or SCHIP-style semantics. If an interpreter is based on reference information derived from "Cowgod's reference", it likely contains the mistakes introduced in SCHIP. Out of the box, Octo behaves mostly like the original CHIP-8, but you can configure it to work more like SCHIP. With care it's possible to write programs that run correctly on both; see the linter I mentioned elsewhere in this discussion.