I have a bunch of cheap Walmart gallon zip lock bags. The FM2100 comes with a great plastic cutter which removes the locking part of the bag which only takes a second to do. However, when I go to suck and seal, the machine removes the tiniest bit of air, then makes a high rev noise, and then stops to seal the bag, leaving about 95% of the air inside. It seals it perfectly. The sealer works on multiple items like chip bags, pasta bags etc. Just not ziplocks. I'd really like to use the cheaper Walmart bags vs buying FoodSaver rolls, which are overpriced. Any idea whats going on or what I can do?