How did you upload the custom firmware? Did you just use the Espruino bootloader to do it, or DFU?
I guess it's possible the bootloader has got corrupted somehow.
I used the command line with the stm32loader.py script.
python stm32loader.py -k -p /dev/tty.usbmodem1411 -evw espruino_1v99.3969_pico_1r3.bin
is what I used.
Also all I changed in the firmware was the Banner to say something else.
@Gordon started
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
How did you upload the custom firmware? Did you just use the Espruino bootloader to do it, or DFU?
I guess it's possible the bootloader has got corrupted somehow.