[Swordmaker]

Consider: just because the container has a refrigeration unit doesn't mean it's being used, does it? Also, it might be for other than refrigeration, possibly a filter unit to prevent something (radioactive?) from escaping the container and being detected. Could also be to circulate fresh air inside to keep someone/something alive.

Overactive imagination?

Not at all overactive. You are absolutely right. Could be used as a filter for clean air, too. But I doubt that anything could be alive inside all that shrink wrap. LOL! I'd suspect sealing tape to keep something contained even more contained.

[pa_dweller]

But I doubt that anything could be alive inside all that shrink wrap. LOL!

Okay, I'll go a little further into the deep end, but no more, shrink wrap is applied to keep the load together and from shifting. It's not applied to the underside of the skid. Hidden air vents?