Probably the most common cause of this is not enough tension on the blade. To get good results when re-sawing, there are a lot of factors to consider. If you have the manual for the saw, see if it has instructions on how to properly adjust and set up the saw. Go through all of those steps to ensure the saw is operating to it's fullest potential. There are probably even tons of YouTube videos you could watch on tuning a bandsaw that might be helpful.
The location of the blade guides and tracking of the blade is also critical for re-sawing. Unfortunately, I believe that the inexpensive, bench top bandsaws are always going to present a challenge when it comes to re-sawing. If it is the 3 wheel version, those are notoriously finicky to get adjusted properly. Thicker (wider) blades can help with re-sawing, but I doubt you will be able to put a much wider blade on a small, benchtop saw. Because the wheels are smaller than on larger saws, it means the blade has to be flexible enough to bend in the tighter circumference. That will limit the width/thickness of the blade the saw will accept. Also, wider re-saw blades require more tension than the narrow blades. Most of the smaller, benchtop saws don't have the capability to apply enough tension for them.
