Some clients encountered serious damages to their products due to humidity issues. For example, some faced: moldy shoes, moldy car mats, unstuck carton boxes, cracked wood furniture, rusty metal (screws etc) and more. In fact there are a range of possible issues including mold, corrosion, deformation, and even functionality problems.

Despite our quality control inspection (we checked their products as per their specifications and all was okay at the time of inspection), some of these issues occurred even after previous shipments were fine. What cause humidity of your imports? 

It could be raining during the loading of the container (rainy seasons in China are long) and some cartons + container floor got wet.
There could have been a hole in the container, allowing rain to pass on.
The container could have been under serious climatic conditions: heavy sun, rain, wind.
The products could have been damp before packing and shipment. Imagine putting a humid product inside a poly-bag with no hole !
The packaging and packing materials were humid.
You should know that fungi, molds and mildew do not usually cause any problems below approximately 55% Relative Humidity.