Transmission problems

I have a 2012 Ford Fiesta and on my way to Texas from Missouri it would not go into gears 1,3, and 5. It stopped as quickly as it started, but 5th gear would just rev the motor. There was no power to the wheels. Then there was the loudest grinding noise (sounded like rocks in the engine) in gears 1,2,3, neutral, and reverse. Fourth gear worked fine. When I returned home I was told the Synchronizer went out and caused the fluid to leak out and the gears were shot. I had the transmission replaced and before I put 50 miles on it the same exact thing happened. No 5th gear, sounds like rocks in the engine (even in neutral) and 4th gear works great. I was told I was sold a bad transmission and it needs to be replaced again. I could really use some advise!