Together with the A7R III, Sony released a 24-105mm f/4 mid-range zoom lens. Months later, it is still on back-order, but the first issues with the lens has already been detected. According to Sony “in certain shooting conditions an out of focus issue may occur with some 24-105mm F4 Full-frame E-mount G (SEL24105G) lenses”.
On their support page Sony released a note describing the problem and giving you the option to check your lens serial number to see if your lens is affected by the issue or not.
Sony will repair all affected lenses FREE until March 31, 2020.
These symptoms may occur under certain shooting conditions:
The lens may not focus when using autofocus with close aperture
The lens may be out of focus when changing the aperture after using manual focus
Check Whether or Not Your Lens is Affected
This only applies to SEL24105G lenses with certain serial numbers.
The SEL24105G serial number is on the side of the lens near the base…”
To see if your lens is affected, please visit Sony Support page.