Robot stops at the top of stairs or dark carpets even though there is no drop; may refuse to cross dark patterns.

Safety first: Keep the robot away from actual stairs while testing.

Clean sensors:

• Wipe all underside cliff sensor windows with a soft, dry cloth.

Environmental adjustments:

• Test the robot on a lighter-colored floor to confirm the behavior.
• If dark carpets cause issues, consider using virtual walls or no-go zones (if supported) to block those areas.

If false detection continues on normal floors: The cliff sensor module may be out of calibration or failing. Replacement of the cliff sensor board is the long-term fix.