LiftMaster 8355W garage door opening by itself at night (repeat) — no keypad/remote use, driveway camera shows nobody

Hi all… looking for help diagnosing a LiftMaster 8355W that has opened on its own multiple times overnight.

What happened:

• Door was found open a few mornings ago. MyQ log shows it opened around 2 AM. Happened again next day at midnight. And happened again at 11 pm tonight.

• Driveway camera shows nobody approached the door, and nobody used the keypad.

My setup / notes:

• LiftMaster 8355W + MyQ app

• Photo eyes are normal: one amber/orange and one green

• Wall control has LOCK button (vacation mode). I enabled LOCK mode earlier today , but the door still opened later. (Also noticed MyQ app can still open the door even with LOCK mode on.)

• Builder installed an interior manual slide lock. I tested pressing OPEN with the slide lock engaged: opener stops within ~0.5 sec (no damage).

• Problem is intermittent/repeatable: it has happened on multiple nights.

• Handheld remote is stored inside the house in a drawer, unused (not in car, not pressed, batteries intact)

Questions:

1. Is the most likely cause a shorted wall control / wiring, or a failing logic board?

2. What’s the best isolation test order? (I plan to disconnect the wall control wires at the opener head next.)

3. Any known issues specific to the 8355W where it “phantom opens”?

4. Any thing else I should check? 
   

Thanks. This is stressing me out because if it opens while I’m away, someone could walk into the garage.