Trane cooling issues

[Makita]

Here's what I got. Trane model TAM7A0C48H41EAA , THERMOSTAT MODEL TRANE XL824.

  I've had technicians out 3 times 3 different ones and last was service manager, same ones that installed unit. Refrigerate is all are good verified by all 3. Air at registers average 53 degrees. Problem is, unit continues to run even after reaching set temperature. Last technician said it was thermostat, well after that chunk of change it didn't fix it. Normally this unit can be turned up during the day while no ones here, and turn it back prior to coming home, unit would cool 5 to 6 degrees in just a few minutes and cut off. Now it gets to set temperature, after while 2nd stage comes on fighting to get thermostat to agree with unit after never being satisfied it returns back to 1st stage. Just back and forth. I can trigger it to cut off by adjusting thermostat above idea setting. That's the issue.
  OK, please figure this out for me, it's a sad world today that the technicians that installed it can't troubleshoot their own equipment. I'm not a HVAC guy, but what I can tell you like I told them 2nd stage doesn't blow as hard as it use to, it use to sound like turbo boost kicked in, it does pick up speed but nothing like it did, by the way last technician seen the problem and it blew his mind, and just settled on thermostat as issue, but  your then outside are Air had already cooled near idea setting. Hopefully I explained it well enough, basically the unit runs like a window unit from 1979. If you need more Information let me know. Thanks in advance!