I strongly recommend to study a little bit of thermodynamics and properties of water vapor.
For some mystical reason, it is often suggested to store moisture-sensitive products in air-tight packaging for cooling in a freezer, but this is completely wrong and absurd if not done right.
Use a dew point calculator (e.g. at
http://www.dpcalc.org/ ) to see how the relative humidity goes up when the temperature goes down
given that the absolute moisture content stays constant -- which is EXACTLY what happens when sealing the warm, possibly humid air inside that package. Reducing the volume of air trapped by using a "vacuum" packaging helps but does not solve the problem.
The absolute moisture content of the air inside the fridge of freezer is always lower than outside, because condensation occurs at the
coldest point, namely the evaporator plate/coil, drying the air, so by sealing the package, you are always making the air inside MORE moist than it would be without any package.
On the other hand, watertight packaging helps with accidental exposure to melted condensate which can happen at power shortage etc.
So, as to provide a simple solution, get some silica gel from Ebay and place a few bags inside that airtight packaging before sealing it! It is dirt cheap and you can regenerate it by heating in oven at about 150C for an hour.
So, why are films originally packaged in air-tight packaging? Just for the same reason. The difference is, they do the packaging on a very dry environment! It has to be done right. You will fail if you have a hot, moist rainy summer day when sealing the packages, and there will be a lot of condensation inside the package on all surfaces when cooled down.