Our freezer is frosting up, when it does that the freezer fan blows either gently or intermittent, this causes the freezer and fridge to warm up. when we defrost it, it well run fine for a few days until the frost builds back up. Had some one come out and open the freezer, no diagnostic just a look and told ups we needed to replace the Adaptive defrost control panel. Should I get a second opinion, what else could it be.
Thanks in advance for your help

That adaptive defrost control is a likely part, but the defrost thermostat is also a possibility. The ADC can fail in several ways. You'd need to do a deeper diagnosis to narrow it down. If you have a multimeter you can do it by testing the whole defrost heater circuit at the ADC.

Barring that you can visually look at the defrost thermostat when it is exposed, it's mounted on evaporator behind the back wall in freezer. If it is bulged out or otherwise looks damaged I'd change it. It'll require some wires to be cut but nothing hard.