Full wave rectifier reached the limit
The second OpAmp has an input common range that ends 1.5V below the positive supply. In this configuration the input common mode voltage is equal to input voltage, the circuit will only work up to about VDD - 1.5V which turns out to be 3.5V

From the datasheet:



You need to increase the supply voltage to increase the input common mode range or pick a different OpAmp.