Is frozen oil a normal phenomenon?

Frozen oil is an absolutely natural phenomenon and it does not prejudice the product’s quality. 
Oil starts freezing at a temperature of about 10 degrees: at the beginning it generates some whitish dots, little flakes, dimming, and a bit of deposit on the bottom of the bottle; then, in case of long lasting exposure to cold temperature, the oil becomes solid. 
In order to defrost the oil, first of all it is necessary to loosen the container’s cap to avoid possible breaking of the container itself, since oil, while defrosting, dilates. Then, you have to put the container close to a radiator or a stove, so that in few time the oil will return fluid and limpid. 
You will get the same result by heating the container with loosen cap in a bain-marie (water should have a temperature of about 40 degrees) and shaking it a little bit. Those treatments absolutely don’t prejudice the oil’s quality. 
You also have to keep in mind that oil can suffer from cold temperatures even during the transportation process: either the oil freezes or not, this fact doesn’t indicate its genuineness.