Diagnosis
Obstructed safety sensor path or misaligned sensors. The 8587w uses infrared beam sensors. Any blockage or misalignment triggers an auto-reverse.
How to Fix It
Check the sensor LED lights. Both sensors are mounted on brackets 6 inches above the floor. The sending sensor (amber LED) must have a solid light. The receiving sensor (green LED) must have a solid light. If the green LED is off or blinking, the beam is blocked. Clean the lenses with a soft cloth. Realign the sensors until both LEDs are solid.
If That Didn't Work
The down force setting may be too low. With the door disconnected from the opener, run a down cycle. If the door moves smoothly, increase the down force limit by one click using the force adjustment screws on the side of the opener.
Heads Up
Do not bypass the sensors by holding down the wall button. This disables a critical safety feature. Sunlight directly hitting a sensor lens can also cause interference.