According to this story, a lower state court judge in South Carolina has ordered the Republican Party to hold a supplemental primary in one legislative district, and a second such lawsuit is pending. The story mentions the federal law that requires overseas absentee ballots to be mailed at least 45 days before any primary or any election, but fails to note that the law only pertains to federal office.

Several other states and territories are holding September primaries, including Delaware, Guam, Massachusetts, New Hampshire, Rhode Island, and New York (but the New York primary is for state and local office, not Congress). UPDATE: here is a much more detailed article.