Hello, investigating your device I found that 1. Q1B is definitelly in reverse connection Are you sure?
2. LMC7101 limits positive output at 3V.
Response from knack.supply | Sept. 3, 2018
Can you please send me a close-up photo of the top side of the board?
1. The Q1B connection issue seems very strange to me as I test all the units before shipping. 2. Yep, the voltage isn't full 5V, but it shouldn't be as low as you say. LMC7101 is a rail-to-rail op amp so you're only supposed to have ≈0.8V drop from Q1 and op amp in total.
Have a nice day!