Diagnosis
The silicone membrane under the control panel button is worn or has debris under it. This is a physical switch issue.
How to Fix It
Unplug the unit. Use a cotton swab dipped in isopropyl alcohol. Press the power button down and run the swab around its edge to let alcohol seep in. Press the button 20-30 times to work the alcohol in and dissolve any sticky residue. Let it dry completely for an hour.
If That Didn't Work
The membrane switch panel is failing. The entire control panel is one sealed unit. It cannot be cleaned further. It must be replaced. Contact Chefman for a replacement front panel assembly.
Heads Up
Do not use excessive force. Do not pry the button off. You will damage the seal and let grease into the electronics, causing a complete failure.