HVAC question

[HeadnSouth]

Nov 2017 we had a new carrier 3 ton unit installed. It has been very hot here in Georgia and on those days the upstairs unit cannot keep the temps at 72F it'll get up to 76 78.
We have had the installation company out a couple of times and they have added freon with the same results.
Now they tell me it's the expansion valve and the coil that needs to be replaced and they want $700 to replace it.
Labor warranty was for 1 year and 10 year's on material.

According to the tech the expansion valve was made with a varnish on the valve and it causes it to stick. Will this problem affect anything else in the system that would cause premature failure?
Looking for a second opinion on this.

[akaothermick]

Sounds more like the unit is undersized for the application, or your insulation and roof ventilation system is lacking and was not taken in to account when the unit was sized. Square footage and insulation and other aspects such as roof deck ventilation can change the ratio when sizing a system. The expansion valve and coil replacement is a possibility but if they do the work without fixing the problem will they forego the $700 charge?, i doubt it, you need a guarantee that if it does not fix the issue you will not have to pay,

[HeadnSouth]

Sounds more like the unit is undersized for the application, or your insulation and roof ventilation system is lacking and was not taken in to account when the unit was sized. Square footage and insulation and other aspects such as roof deck ventilation can change the ratio when sizing a system. The expansion valve and coil replacement is a possibility but if they do the work without fixing the problem will they forego the $700 charge?, i doubt it, you need a guarantee that if it does not fix the issue you will not have to pay,

Got a call from the installation company. They are going to eat the installation cost. They have been out a half dozen times to try to fix the issue since the install.
Btw we had a 2 ton unit and they increased it to a 3 ton and added some returns.
Hopefully this will fix the issue.

My main concern is will the contamination affect the compressor or any other components?