I bought a food saver a few years back. It has this nasty habit of letting what I consider to be a significant amount of air back into the bag. I foolishly thought I could live with this problem, but now understand that it might as well go back to the zip locks. My model is the stand up type so there is no way to manually compress the clamp to prevent air coming back in. I presume you can do that with the clam models (my term but I hope you get my gist).
Do most food saver brand products have this issue. Is there a preferred vacuum sealer out there?
I have a Vac 500 model that is of the clam shell design. It performs well with a quick switchover from vacuum to seal. The biggest problem I have is getting it to vacuum if the bag is somewhat full. I sometimes place something under the bag to elevate it a little to aid in the vacuum process. As sedimental said a dryer interior near the top is better.
I have the same stand up kind. Mine does this occasionally too. I notice that it does this when the inside top of the bag (where it would seal) is wet or damp. My machine is particularly sensitive to this. I now make sure that I dry the inside (and outside) of the bag thoroughly with a paper towel first before sealing. When i take care to do this- my machine "sucks the dickens out" of the bag and I have a great vacuum seal. Hope this helps.