The wiki doesn't have a detailed article on the Fanatics Fest backflip incident itself, but it's referenced as a July 19 news item titled "Cam Skattebo’s failed Fanatics Fest backflip tempts fate" (from the John Harbaugh page). There's no report in the wiki of a new injury from that backflip — the landing was reportedly rough, but the existing medical outlook (updated July 16) still projects him to play Week 1 with no limitations.
That said, the expert reaction has been notable. On Establish The Run, Evan Silva said "I didn't like the way that he tried to stick the landing" (). And on Late-Round Fantasy Football, the host said "the backflip did a lot for me... That is a lot of force on that leg" () — both view it as a red flag worth monitoring, though no one has reported a setback.
So the short answer: no confirmed injury from the backflip, but it's put the spotlight back on his durability concerns heading into camp.