I also own a PT709 Slim, with over 500 rounds through it, in less than a month. I have had zero problems with the gun. That includes use with +P and +P+ ammunition. Many other owners of the same guns have the same record. If there is a "possible design flaw", why hasn't anyone else reported it? If it hasn't been noted, why would Taurus admit to it? Are you a gunsmith with a background in design?
March the 18th was a Sunday. The week of March 18th ran all the way to the 24th. So, they have had the gun approximately three weeks. My experience with other manufacturers, to include Sig, HK, and S&W, is that repairs typically run around 6 weeks. At that point you get the gun back, fixed or, all too often, not.
It is a good thing that you have more than one gun for carry. After all, if you have to actually use it, the police will own it until the investigation is done. Those who only have one, are left unarmed. In today's world, angry relatives, other gang members, or even friends of the accused, may come to visit.
I use a performance based criterion for CCW guns. Repaired or totally new, if it passes the 300 round mark, I carry it. Otherwise, It would be very hard to carry anything. Great guns age with use, and can become unreliable until repaired. If that were my criterion, to never trust a repaired gun, there would be plenty of guns sitting in the vault, but not available to me. I find it inexplicable that people will send back a S&W, Kimber, Sig, or HK for warranty, and place it in service afterwards without a second thought, but will forever distrust another brand.
Wait for the repair to be accomplished, shoot the gun in for your personal break-in, and see what it does. Good luck,