Correct me where I'm wrong:
During the cruise, the CT pumps are switched of when reaching 900 kgs. Untill the wing tanks are 50 % empty, these 900 kgs remains in the CT, cooling down much faster than in the wings. Some of this fuel might freeze, and not be transfered by the scavenge pumps. During the descent, the remaining untransfered frozen fuel melts in a kind of slush. If for some reason the CT right pump was on, then this mix would have been transfered to both engines (via the X-feed that was supposed to be open according to the previous report and statements of the crew). This would explain the similar reaction of both engines, provided with slush coming from the same location. The 7s delay might be explained by the longer distance to reach the left engine than the right from the CT right pump.
Question, how can this CT right pump be operating during the approach ?