Oblique Repair for Abdominal Bulge After Diastasis Repair?

The fascia over the oblique muscles is weak. It is not, in my opinion, totally reliable when tightened as one does in the center of the abdomen. We have abandoned oblique repairs for that reason during tummy tucks.
Better in my opinion to tighten the center (diastasis and central tightening) more aggressively where the fascia is strong.
Remember, when fascial tightening is performed, there are limitations to its success. If the fascia has lost its elasticity, either congenitally or through various diseases, tightening of the fascia does not necessarily make a flat abdomen... just a flattER abdomen. You still have the original fascia with all its elastic properties, just a tightened version of it.

If you still have laxity of your muscles after tightening of the rectus muscles, oblique tightening may help. I often do this during the tummy tuck which adds additional support but also increases pain post operatively. If your rectus muscle is truly intact and tight, then this may be the way to go.  

The real question is not the direction of tightening but if tightening will work.
If you take a tube of toothpaste (with the cap on) and squeeze the tube, the paste moves to another part of the tube not under pressure. This is similar to what you may have. If your doctor tightened you as he or she should have- regardless of the technique, the intraabdomenal contents has to go somewhere. Without an exam or photos it is hard to make an accurate diagnosis, but I do not want you to be disappointed with another sub par procedure.