Once a patent is issued, it is exceedingly rare for it to go through additional review unless there is litigation that prompts it (re-exam, IPR, etc.) Separate

Once a patent is issued, it is exceedingly rare for it to go through additional review unless there is litigation that prompts it (re-exam, IPR, etc.) Separately, it's quite common for people to patent things that don't work or can't be directly implemented as stand-alone things at all. Indeed, defendants in patent litigation often point out the many early patents on "flying machines" as proof that the issuance of a patent is not proof that it would lead to a working thing.