Diagnosis
Moisture or sticky residue has seeped under the membrane touchpad, causing electrical shorts.
How to Fix It
Unplug the blender. Wipe the entire control panel area with a cloth dampened with isopropyl alcohol. Use a cotton swab around the edges of each button. Let it dry completely for 30 minutes before plugging back in.
If That Didn't Work
The membrane switch panel itself is faulty. Liquid damage is common. The entire control panel assembly would need replacement. This requires disassembling the base.
Heads Up
Never submerge the motor base or pour water directly over the control panel. Clean it with a damp cloth only.