This is my second 502 Hero that has this widely reported defect, whereby the left-click button double-clicks occasionally upon a single press. Initially, this happens about 5% of the time and then increases to as high as 25% of the time, making the mouse virtually useless.
Logitech replaced my first defective 502 in the summer, but their replacement has failed again in just three months.
DO NOT buy this model, and I would personally recommend avoiding Logitech until the company is willing to acknowledge this flaw and to stop using cheap switches. My old Proteus Core was perfect for many years, as it used superior switches, before Logitech sold out to a cheap supplier.