Do you know if your thermostat is meeting the setpoint?
What do you have it set at, and what temperature does it say it is?
This sounds like your evaporator may be icing up.
Have you checked your air filter?
It is the inside part of your air conditioning.
The evaporator will be mounted with the furnace.
If the evaporator is iced up it is either lacking air flow, or lacking refrigerant.
I would try using a shop vac to clean out your drains. This will eliminate one source of a problem.
Do you think your evaporator is icing up?
An evaporator will ice up if it does not have proper air flow, such as a blower motor going out, or shutting off from overheating. A dirty filter, or evaporator coil would also reduce airflow.
Also, the evaporator will ice up with there is a loss of refrigerant, or the metering device is restricted.
Since you have had this system check, the companies should warranty thier work.
The thermostat could be off calibration.
Or a safety device would do that.
As an example a pressure switch would keep the system from running the condenser.
Or a safety on the drain line.
If this problem happens at the hottest point of the day I would start with the high pressure switch, but not all systems have one.
Some systems do not have any safetys at all.
HVAC Technician
EPA issued refrigeration license, College certificate, and 7 years in field.