Two red flags are his foot and his maturity.
As a guy who broke his navicular bone, I can tell you that setbacks are normal and at 9 months later I still have some soreness and weakness. It is one of the most difficult injuries to recover from.
On top of that, many medical experts think that people who break their navicular bone often do because of structural things. Weak ankles combined with a longer second toe lead to added stress on my navicular and created a nut-cracker effect. In other words, it could be a recurring concern, but it also may not be.
Embiid had reports of knee and back issues. My unprofessional guess based on my experience is that he did not do strength training appropriately, which led to structural weakness in his core and added strain on his knees. When he got back to it, the weakness was still there, but it led to further stress on his ankles and navicular bone, causing the break. His impatience led to the rebreak (trust me when I say that impatience is normal with navicular breaks), which led to setbacks and an inability to work on his body. A solid training regimen could be the only thing necessary to get him read.
This is not the same kind of broken foot as Yao Ming's stress fractures though.
My concern has more been his relative lack of maturity, although I'm willing to roll the dice on that talent if the doctors think his foot is fine.
