The Techs have told me that the way the flexible pipe is routed, it is creating another "P-Trap" behind the cabinets. I intend on eliminating this (If I can). I think that portion of the drain would be very difficult to winterize effectively.
We didn’t have a problem with our sink draining on our FE but it wasn’t fully secure and ended up on the heater and melted. Of course this caused it to leak everywhere. It may be your drain pipe is getting binding up or has collapsed some. The drawer under the stove allows you access to the pipe. Good luck the pipe also goes through the side of the slide wall and into the bathroom so there are a couple of places it could get pinched.