Good heat seals are the product of the right combination of heat, pressure, dwell time and allowing the molten plastic to cool down in a relaxed state.
Leakers result from these conditions gone awry. If you are getting good seals in some areas and bad seals in others, it’s not the film. The film is the same all over.
Before downloading the troubleshooting guide and getting into the specific causes and remedies on F/F/S equipment, take just a few minutes to review the fundamentals: