There is a limit to how much "Cool" an absorption cooling system can provide. If it's too hot out. and too hot in and the sun is beating down on it. You may have an issue.
Adding cooling fan(s) may help.. Mine is in the lower compartment blowing UP. I have a single Computer type fan (4") in the compartment. Tight fit. I may put in a 2nd one later. Blowing UP through the condenser and out the top. Mine is not in a slide so it blows out the roof. You can also put 'em in the top sucking air. but I like it better in the bottom where I don't have to climb a ladder.