Engine Stall problems of the 2019 Subaru Impreza Wrx

The vehicle stalled at highway speed as I began to decelerate on the interstate highway. I attempted several times to restart the engine until the vehicle reach a rolling stop in the middle of the 4 lane highway. I turned on my hazard lights and after approximately a minute I managed engage the engine for a brief period to reach the shoulder of the highway before the engine stalled again. There were no indicators or warning lights on. I tried several times to start the engine with no success so I called for service. After waiting for 30 minutes, I tried to start the car again; this time the rpms stayed normal. I drove to the car dealership for service. On the first day the technicians were able to replicate the issue but could not identify anything wrong with the vehicle. The technicians tested my fuel octane and electrical system. The technicians then ran a full diagnostic test on the car and still they could not find anything. My vehicle has been with the Subaru technicians for 6 days and so far the problem is still unknown.