Each fixture drain has a trap to prevent sewer gas from entering the home. Each drain has to be vented after the trap. These vents are then vented to the outside through the roof.
When the roof vents get clogged, or partially clogged, with birdnests, leaves, debris, etc., they do not allow the drains to function properly and it creates a siphon of the water from the nearest trap for a "vent" when water drains through the lines, such as your washer.
Go up (or have someone else do it) on the roof and clean out all debris that can be reached by hand from the vent pipes. Then snake the vents with a heavy duty plumber's snake to break up the debris, if any, if necessary. Then flush the vents down with a water hose sprayer.
It should all just flow right out into the sewer and clear your vents, solving your problem. Sometimes just flushing it down with a water hose will do it.
Good Luck!
Mike