Polling or interrupt on a custom module signal???

Does your component waits until the value was read before providing a new one to the CPU? It may be a good idea to look what's going on in your component using SignalTap.

Using interrupts is mostly a performance improvement, as it allows the CPU to do something else when data isn't available, instead of polling continuously. But you should first find out why you get the wrong data before thinking about using interrupts.