First of all, what, exactly, do you mean by "checks OK," and secondly, what has the ICE to do with it?

I think you're making this too difficult.

If you plug the OKI part into the 8032 board, regardless of the EPROM in its piggy-back socket, it should behave exactly as the 8032 does, at least superficially.

Just for a baseline experiment, why not try that? Presumably, the 8032 board, with its original EPROM and MCU, works properly, doesn't it?

When you're finished verifying that the OKI part behaves as the 8032 does, you should take the EPROM on the 8032 board and plug it into the piggy-back socket, if it's a compatible EPROM/ROM (the OKI part doesn't require that it be an EPROM, as only the pinout matters) tie the nEA signal high, and see whether the OKI part, again, behaves as the 8032 does.

After that, plug your original EPROM, not the one from the 8032 board, into the 8032 board with the 8032 in place. See whether that works as you expect. I suspect you'll find it doesn't, and that will show that the code is at fault. It's probably not difficult code, but it's easy to fool yourself.

RE