Possibly OnSemi NCP585DSN33T1G - a 3.3 V LDO rated for up to 350 mA output.
Based on the datasheet linked above the part is marked with a five digit code where the first three digits are the part specific marking, R33 in this case, and the second two digits are a traceability code.
The part has the following pinout. This matches with your 5 V being Vin (pin 1), 3.3 V being Vout (pin 5), and GND (pin 2).
Pin 3 is an output enable, which being a pulled up to 3.3V makes sense as this is the active high variety. The Eco pin seems to be some internally generated bias, so a weird voltage makes sense.
The part has an upper limit of 250 mW power dissipation, which would limit the current to under 150 mA for a 5 V input. While the junction to ambient thermal information is not specified, I assume this power limit is a thermal limiting factor, so getting hot is not entirely surprising.
As long as the temperature is less than the 85 °C rated maximum operating parameter, the part should be functioning normally and this part is likely not the culprit to your incorrectly operating device. The fact that it is still successfully regulating the output to the correct level further supports that.