We bought a used SLC500 (1747-l40A) from a vendor. Comes with one year warranty. It's still on our test bench. I downloaded a program to it and verified every I/O terminal and comm with HMI. However, once in a while, its CPU fault LED comes on for a second. Then it goes away & PC RUN LED comes back on, and everything working again like nothing happened. I should return it, right?