LV won't provide 12V
Wiki says that the regulation range is 5-12V. But LM317 has a high dropout voltage. It will hardly reach 11V. Even with DAC3=2.5V, the IC6 will try to output 2.5* (51/10+1) = 15.25V which is out of its output range so will clip it to the supply rail. Please correct the IC6 gain. Or, better just use PMOS instead of RG1 and make standard LDO working from 5 to 12V.