Why do Some SL Lens Lock Buttons Break & Some Don't ?
I talked to the son of the plastic lens lock button's designer. He said that the button's metal "stem" needed to be inserted into the red plastic while the plastic was heated into a liquid form at a specific temperature. If the stem was inserted too soon or too late then the plastic would eventually crack. So if your SL camera still has its red lens button its a good one. 3rd photo shows lots of good red buttons that people wanted replaced with the all-metal buttons even though these red buttons are still good. I still have the all-metal release buttons in stock if your button is cracked.