The fuel pump O-ring may have been twisted during installation, causing a gas leak.
The recall affects a total of 6,928 examples of three models: the 2017-2018 DL650, the 2017-2018 GSX-R1000, and the 2018 GSX-S750. Despite having different engines, in all cases the design of the fuel pump O-ring and fuel tank inner vessel can allow the fuel pump O-ring to be twisted during the fuel pump installation process. This seems to be a design flaw that allows this problem to occur rather than improper installation by the factory.
Under the recall, Suzuki will replace the fuel pump O-ring and fuel tank inner vessel with improved parts to prevent the O-ring from getting twisted. The recalled fuel pump O-ring has a D-shaped cross-section, while the replacement O-ring has a round cross-section. Suzuki has also added ribs to the replacement fuel tank inner vessel, which the recalled inner vessel does not have.
Any owners who have already had this problem repaired outside of the recall may be eligible for partial or total reimbursement of repair expenses by Suzuki. NHTSA has a document on its website containing details, but essentially, contact your dealer and they should take care of you.
Unfortunately, the $100 incentive to bring your Gixxer in for recall service doesn't apply to this recall, only to older bikes. It is a mystery as to why the Wee-Strom, which has a V-twin engine, and the two Gixxers, which use inline-4s, suffer from exactly the same problem. Possibly their fuel pump designs are similar enough that Suzuki used the same basic designs in each, which led to this problem affecting all bikes using this design.