reTerminal - not booting when powered via GPIO

Hi, I seem to have hit a strange problem with reTerminal.

If I power reTerminal via USB-C connector (5V/3A power supply), it boots just fine and the screen comes up.

Now, if I power via the GPIO header (pins 5V/5V/GND - 2, 4, 6 respectively) the PWR and SYS LEDs light up, then the SYS LED briefly flashes (then stays on), but that’s it - it will not boot further, the screen is also visibly off (and not a black screen, but with the backlight on). I can also feel the back heatsink getting very hot as if the CPU is stuck in a loop pegging it at 100%.

However, if I connect an external HDMI monitor to the micro-HDMI connector, the terminal does boot just fine. If I disconnect the monitor – it even continues to work! But then if I decide to reboot or power off and then on again (without the monitor connected) – same problem arises.

I am very perplexed by this. The power supply connected to the GPIO header is a well-known, stable, lab bench power supply that sees very minimal voltage drop (in the range of 100mV at most) but keeps the power stable at 5V.

After some additional experimentation I discovered that I had to bump my bench power supply to (a whopping) 5.3V and now it boots and the screen works. Very strange as a slight over-voltage seems unnecessary.