Franzfume Though it would be disruptive, it might be diagnostic for you to flash the device back to Google's OS and try taking pictures. If Google's OS crashes when it tries to take pictures, then most likely the camera is broken. If taking pictures works fine on Google's OS, there might be a bug somewhere in GrapheneOS.
Alternatively, you could try collecting a crash dump after a crash. Here are some directions: https://discuss.grapheneos.org/d/302
But if you have just started using the device it might be most straightforward to see whether it crashes while taking pictures using Google's OS.