Mystery Solved!! I have a Brother LS-1217, and had same problem with needles falling out when using a walking foot. Then I discovered the Needle Clamp screw (which holds the needle) is actually too short to use with special presser feet such as a Walking Foot. At "SewingPartsOnline" I purchased a special longer Needle Clamp for $3.99 ("needle clamp attachment screw #SKL-1) I had really pulled my hair out trying to solve this.
Last edited by QuiltnNan; 11-10-2017 at 09:58 AM.
Reason: remove shouting/ all CAPS