Sony reported that some units of the FE 24-105mm F4 G OSS (SEL24105G) could exhibit two symptoms under certain shooting conditions: the lens would not focus when autofocusing with the aperture closed down, and the lens would be out of focus when the aperture was changed after focusing manually.
Affected lenses, identified by serial number, were repaired free of charge until 31 March 2020.
Because both symptoms require a specific sequence of operations, an owner who habitually shot wide open could have used an affected copy for years without ever seeing the fault. This is a good example of why ownership reports record the circumstances of a failure and not just its presence.