I just looked over each foil packet of replacement tinder that UST sent me recently... I can't find any obvious seam or packaging failures on the individual cubes.

When stored in an airtight container (such as a Lock 'n' Lock) the WetFire tinder seems to be offgassing some sort of byproduct. It collects on the wall of the plastic container and leaves a cloudy, slippery film. The smell is definitely of the chemical variety. I'm assuming since the tinder is non-toxic this is nothing to worry about.

This offgassing happened with the original batches of WetFire that had seam failures, and also with this newer batch with no seam failures.