Should I consider this 1.57V open pull-up pin on ESP32 faulty?
I had in the past a similar problem.
In an NXP LPC2388 powered at 3.3 Volt, a couple of input pins programmed as pull-up pins with nothing externally attached, showed 2.4 Volt instead of 3.3 Volt.
I read carefully the datasheet of the microcontroller and realized that the minimum output voltage of input pins programmed as pull-up was 2.4 Volt.
I suggest you to read the datasheet of the ESP32.