Canon has acknowledged that a glitch in the recently released EF 40mm F2.8 STM pancake prime can cause autofocus to stop working. At present, if pressure is applied to the front of the lens when it's attached to the camera (which can include re-attaching the lens cap), the autofocus may stop working. The glitch can be overcome by dismounting and re-attaching the lens or by removing the camera's battery briefly. In its product advisory notice, the company says a firmware fix will be released in late August.