The eyes won't close properly, leaving them open to infection.

This castle hadn't even been properly closed by the last person here!

Someone could get in a door that wasn't closed properly.

The valve may not be able to close properly, so blood can leak through.

Doors that won't close properly may be out of alignment.

It seems that the outside door to the street hadn't closed properly, and they had sneaked in.

Once filled, the tank is a challenge to close and lock properly.

Damned if I know what they're up to, but the first thing to do is see that you're properly closed down for the night.

So who ensures that these dangerous sites are properly closed up?

Structural problems with the eye lids that don't allow them to close properly.