Bags shipped with Chamber Sealer don’t seal

Just got my new Chamber Sealer and tried sealing some dry cereal in one of the bags that was included with the sealer as a test. I set the Seal to Strong. Afterwards, the bag looked sealed - I could see the two melted strips. But when I picked the bag up, the seal immediately broke open. I then tried sealing again, setting a custom seal time to the max setting. This time the seal held.

I would expect that the default “Strong” sealing time should be enough to seal the bag, so I’m wondering if my device is defective. Has anyone else run into this?

Incidentally, I also ordered a supply of the 100 sealing bags that Anova sells on their website and noticed that these bags are much thinner plastic than the bags that were included with the Sealer. Maybe the “Strong” seal setting will only work with those thinner bags, but not the thicker ones?

I don’t remember what bags were included with my chamber sealer. I have ordered a bunch of Avid Armor bags at the same time I ordered the sealer, so I’ve been using those exclusively. I don’t think I had to use the Strong seal setting at all, I keep it on normal and I never have a problem.