The ultimate amount of CO2 in the ale only depends on the pressure and temperature. Since your kegger isn't running much, there probably isn't much air circulation inside. How cold is it in the garage? If it going below 34F at night, bottoms of the kegs will be colder and absorb more CO2.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk