Well, the factory reset is the thing that will clear up a temporary error, but be aware that you have part of your programming that is stored on failing electronics. This could stabilize and last for years and not worsen, or it could potentially continue to degrade. That's what you're up against. It won't hurt the piano to use it in its current state, but your ROM may continue to deteriorate, it's impossible to tell for sure.
Here's how the ROM works:
ROM is programmable, like a flash drive. The only difference is ROM is Read Only Memory, meaning it cannot be re-programmed. The ROM contains the operating system, different sounds, it's what loads parameters when you push different buttons, it's the long term system memory. If it continues to "forget", you may run into more problems.
Long story short, you're able to continue using your piano, normal use won't hurt it any worse than being in storage. Keep an eye out for other abnormalities, and if it starts to go out, we'll need to find you an electronics shop and a way to ship the chips to you. I'm not sure if this helps, but there is a Kurzweil shop in Brazil, +55 (11) 3527-6900. They will be the ones who can get you new ROM chips. They take about 2 hours to replace.