Retaining Wall Repair: 7-ft Cinder Block Over Old Wall—Fill Gap or Not?

Question: 7-ft cinder block wall installed in front of bowing old wall. 5-inch gap. Fill with gravel, cement, or leave?

Answer: New Wall Likely Underbuilt—Gap Fill Won't Fix Structural Flaws

Was new wall steel-reinforced in cores, grouted, on substantial footing (30"+ into backfill)? Old wall behind suggests not.

Without steel + tied footing, new wall will fail as old wall pushes it. It's a free-standing board.

Gap: close off from critters. Concrete might add strength but doesn't fix missing engineering.

—Marc