When initializing the camera I get:
E (34460) gpio: gpio_install_isr_service(409): GPIO isr service already installed
which produces a fatal error in camera.c of the esp-idf esp32-camera component.
I transformed this into a warning without dropping out of the initialization procedure. Like this things seem to work.
I am trying to port the esp-who project to micropython and I extended your micropython c-module (modcamera.c) quite a bit, adding all the functions needed to control the camera (colorbar, hmirror, vflip ...) If interested in the code, please let me know.