Non-working, or intermittently working keys are most likely due to a glitch in the connection between the OP-1 Keyboard and the rest of the unit. If you want to try to fix this yourself then we suggest that you follow this guide. Basically start by removing the keys to uncover the screws, unscrew and lift the keyboard module, then remove and reinsert the connectors. Sometimes this resolves the issue, at least temporary, and a keyboard replacement is not needed. Good luck! Please note: You will void any remaining warranty by doing this.