[rondeo]

Understanding the problem starts with getting the transmission diagnostic trouble code(s). The dealer should have those.

If you are prepared to see for yourself, you can get a bluetooth OBD2 adapter like OBDLink MX for about $150 and use the $5 Forscan app.

Dealing with the Ford dealer system is another matter, others may help there.
Maybe get a second opinion?
You should at least know what the trouble codes are to start with.