I had the same problem. I am not sure what triggered it. I suspected a Bluetooth disconnect during app upload, but that was just a guess.
I have performed a factory reset which solved the problem for several weeks. It occurred again today. I have not uploaded any apps today, but I have compacted storage today. This may have been a coincidence though.
I also use Gadegetbridge (latest version) and I use the apps from https://espruino.github.io/BangleApps/
I have attached the device info from https://espruino.github.io/BangleApps/?c= (maybe we can find a pattern)