The only way of satisfying the condition of the slats is following a full inspection of them of course. I'm not sure from what you say if the engineers have done this.
You say the slats deploy during the turn at: "less than 70 kts" what do you mean by that? The slats should not be activating at speeds around seventy knots.?
I would not expect the slats to deploy until approaching the stall. The slats are aerodynamic and activated by the angle of attack. They are a fantastic and reliable indicator of the approach to the stall. The wing drop to the left during a turn to the left is symptomatic of a stall. HAVE THE ASI CHECKED BEFORE YOU FLY AGAIN, this is quick and simple check for the engineers to perform and could save your life.