Hi aloranca0450,
Welcome to the HVAC Group!
When the ambient conditions are high the condenser must work harder and cannot remove the heat as quickly as it should. In turn the evaporator is not absorbing the heat as it is required to do. Many other things play a factor in the operation of a freezer/cooler including, fan heat, heat leak through insulation, heat load due to trays, pallets, etc. , heat load due to de-frost procedure, heat load due to infiltration, and heat load due to internal lighting, plus you have the items and the number of times the door is opened and closed per day. I have came across similar situation previously and it was necessary to add an additional defrost period, because what was on the system I had were all time initiated/temperature terminated. Try adjusting your defrost times and/or adding an additional one.
Good Luck!