DIAGNOSIS The range is losing power to its control board memory. This usually means the little backup battery on the main control board is dead, or there's a loose connection.
FIX The battery is soldered onto the main control board. To replace it, you need to pull the range out, unplug it, remove the back panel, and pull the main board. It's a standard 3V lithium coin cell (like a CR2032). You'll need to desolder the old one and solder in a new one.
IF THAT DIDN'T WORK If a new battery doesn't solve it, the main control board itself has a problem retaining the memory and likely needs full replacement.
HEADS UP This is a board-level repair. If you're not comfortable with soldering, you're looking at a whole new main board, which is pricey. Some folks just live with the blinking clock.