There doesn’t appear to be a built-in button lock on the YN560 III for preventing accidental power changes. Based on the community response, the practical workaround is a physical one: add a small raised barrier near the directional pad so stray contact doesn’t press the buttons.

Simple DIY options include:

• a bit of putty or a sticky bumper below the buttons
• a small plastic ring or washer-shaped spacer glued around the button area
• stacking thin pieces if you need more height

The idea is to recess the buttons slightly or make them harder to hit unintentionally, while still leaving them usable when you actually want to adjust settings. If accidental presses happen often during shooting, this kind of guard is likely the easiest solution.