Hexadecimal value 0x0B is an invalid character

Happened twice, both times when changing ambient atmosphere colour, noon and dusk colours, happens at random as i've done the 1st step below around 15 times to 15 different objects1. Change ambient atmosphere, noon and dusk colours to random colours (these are the ones I used: Noon: FFF2A2
Dusk: A6DFFF
Ambient day: FFF0C9
2. game randomly refuses to save the planet, and will unload it once clicking off the game/trying to load a planet