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Soils Reports - Real situation

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Fellow Listers, I would appreciate your opinion...
About 12 years ago, a friend of mine - against my advice - bought a brand-new house built on a wedge-shaped fill supported by an about 12-ft retaining wall in the back.  A concrete patio was poured against the back wall footing of the house (slab-on-grade), about 15 feet away from that retaining wall. 
About 8 years after the construction, a pronounced gap developed between the patio and the footing.  On my insistence, my friend contacted the builder, who hired a soils engineer, who wrote a report stating that everything was just fine and normal.
In November of last year, I marked a point on the patio as being 130mm away from the footing.  Last Sunday, that point was measured as 133mm away.  This means that on the yearly basis the patio (and backyard, and the wall) moved away from the house about 5mm.
The point is that the total movement (gap) is about 42mm (3.5mm 12-year annual average), indicating that last year the movement was 42% faster that the average.
The house is OK, except for some cracks; the block property walls perpendicular to the retaining wall exhibit considerable (1.5"-2") distortions.
I talked about the situation with a friend of mine, a very prominent, knowledgeable, and sharp geotechnical engineer, and he did not appear to be too worried about the situation.
What would be you take on this?
V. Steve Gordin, SE
Irvine CA