a/c stop working went to dealer in Georga and the couldnot reproduce the problem last apr 2019 coming from Floriday now July 2019 did it again in Pa.
Try to take it in when it is not working. I know that can be difficult.
Since it is out of warranty consider looking for an independent AC shop.
Could simply be a blend door sticking. Do you ever hear a clicking noise when switching from heat to defrost or to vent positions?