Reverse Current building up Voltage
the LDO may look like this.
The only path for the 16uA is thru the feedback-loop divider resistor chain.







simulate this circuit &ndash; Schematic created using CircuitLab

Normally the opamp, itself wired in non-inverting operation because the PNP
power dissipation device (that bipolar with emitter wired to Vunreg) is inverting, implements a negative-feedback servo-loop regulator-loop with the inputs to the opamp being within a few milliVolts (perhaps even 100 uV or 10uV) of each other.

But the regulator is not designed for 2-quadrant operation  or 4-quadrant operation. (Kepco did make 4-quadrant power supplies; usually those are called "Power amplifers".)

The regulator expects to provide output current. As you can see, 16 UA entering the "Vout" node is too much; the output voltage divider (the feedback divider) cannot sink that much current and the opamp+PNP lose control of Vout.

The opamp output goes up close to Vunreg, shutting off the PNP because the emitter-base voltage is within 0.1 or 0.2 volts of Vunreg; you could build the opamp of bipolar transistors, and achieve that behavior.