Transistor not cutting off at 0V
When the voltage at the gate of the transistor is 3.3V, the transistor goes into saturation, and the voltage at TP8 is close to 0V.

When the voltage at the gate of the transistor is 0V, the transistor goes into cutoff, and TP8 is left floating. I was expecting it to read 3.3V, given that one pin of it is connected 3.3V via the current-limiting resistor, but that's not the case as there's a diode in the between, isolating TP8 from 3V3.