I developed a PCB for a project I'm working on. Today after assembling I tested everything and all relays where working as well as the ESP32 itself. Then I connected the sensors and it stopped booting.
After rolling out the problematic sensor I found that a water sensor that works like a button stops the ESP32 from booting when plugged in when I connect the power, but if I connect the sensor after the ESP32 has booted it works fine.
As a side note: I also noticed that the ESP32 was getting hotter, but not overheating at all, just a bit more warm than I would say normal.
Here is the schematic (VCC = +5 VDC):
I'm using pin 25 for the sensor and from online research I found that pin 25 should be OK for anything and technically shouldn't interfere with the boot up.
In the schematic I had a pull-down resistor of 1 kΩ; I also tried using a 10 kΩ resistor, but no luck.
I tried removing the pull-down resistor altogether and also tried activating the internal pull-down resistor of the ESP32 using software, but still no luck.
I'm using a Raspberry power supply, so 3 A at 5 V, and using a multimeter at the 5 V pin on the ESP32 shows around 6 V being received by it, so I think I can rule out the internal diode voltage drop that some boards have.
Also tried a 10 kΩ pull-up resistor between GPIO0 and 3.3 V but that didn't do anything either.