On my 2012 car (same QR adaptor), there are two points at which the adaptor clicks into place, one further back (about 8-10mm) than the other. In the rearmost position, the wheel can slide a small bit fore/aft, i.e. it's doesn't feel completely secured. In the most forward position the wheel is very secure.
Studying my car, I would say your wheel is still not properly secured. The locking balls should be in that rounded groove visible near the weld in your photo. I believe that at the moment the locking balls are clicked into the bevel sided groove that is rearward of the rounded groove.
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