Remember, the computer just sees an ipac as a keyboard. That's all it thinks it is really. So, if keys aren't working in certain games/emulators, it's likely a software side problem and not something with the ipac.
I can't speak to all retroarch cores - but MAME, for example in retropie, seems to keep both its keyboard bindings AND the bindings you choose on first setup. That could cause conflict. You can see what controls MAME is trying to use by hitting TAB to open the menu while the game is running. There might be similar options for other cores.
If you're still concerned it's an ipac issue, just open up notepad and start hitting keys. Does what you'd expect to happen, happen?
Good luck!