2015 Ford Fiesta P0805 Code: Transmission Stuck in First Gear During Braking

While braking at a stop sign, my 2015 Ford Fiesta unexpectedly lunged forward instead of slowing down. This caused me to swerve into the ditch to avoid colliding with the vehicle ahead. I have long experienced transmission issues, and after this incident, my car would no longer crank or start—also, reverse gear was completely unavailable. These symptoms may be related. My Ford Fiesta is equipped with a DPS6 powershift transmission. During braking attempts, it engaged and remained stuck in first gear. A diagnostic check revealed fault code P0805. I replaced the Transmission Control Module (TCM) as a repair solution. However, if this was not the correct fix, what other symptoms might indicate an incorrect diagnosis or underlying issue? I'm seeking clarity on whether P080或 related transmission problems could cause such behavior and what signs to watch for when troubleshooting this fault.