Flashing blue in the core?

Sometimes my core would start flashing blue, even I reset it still flash blue continuously, the only way I could turn it back is to go to factory reset. firstly I don’t know why it happens sometimes, and it is very annoying if I put it into the product, it would become very problematic for the consumers to use, I don’t know if there is a way to avoid it.

This could mean that it does not have wifi credentials, or if you are using manual or semi-automatic mode and are not using WiFi, it can also mean that your user code was built for a different system framework version. You should update the system modules, I have ran into this myself.
Run make all program-dfu in the modules subdirectory.

I am using the semi-automatic mode, and I have put the credentials into my code.