The spring in those scissors can wear out over time. I don't know about now, but Fiskars used to send replacement springs if you complained.
In your case, I would suspect that lint got caught between the blades. Oil would lubricate that area and cause the lint to become less binding. I think sewing machine oil would last longer than vegetable oil.
Did your son take the blades apart to oil? Because of the spring action, it's probably possible to take the blades apart to clean and oil before re-assembling.
Any metal parts that move against each other can need oiling to help with the sliding action. This includes the pivoting area of a pair of scissors.
Last edited by Prism99; 07-06-2014 at 11:19 AM.