Muscle Repair Failure or Residual Fat? And why do I have a scooped out look on lower stomach? (Photos)

Thank you for your question and series of photographs and I am sorry that your results have not been what you anticipated.  It is difficult without an in-person examination to determine what may be taking place.  Most commonly this is residual swelling from surgery which will spontaneously resolve over the next several months but it would be important to voice your concerns to your surgeon to ensure that other issues are not taking place as you mentioned - discrete fluid collection, muscle laxity, or residual adipose tissue. 

Appears as very acceptable early result. Maybe the expected wish results are unrealistic? Best to allow 6 months healing before thinking something is wrong.

The area around the belly button has a propensity for retaining fat even after aggressive liposuction.Because surgeons worry about the survival of the belly button during a tummy tuck there is a tendency to be conservative with liposuction in this area, which is sound surgical thinking as its much easier to do a touch up lipo than to reconstruct a dead belly button! You are still early and a large part of it might just be swelling. I think the idea of muscle repair failure is less likely than swelling or residual fat. You're going to have to wait this out a little longer.