Takes long to open a world, display its contents and saving

Starting from yesterday I noticed that a takes minutes after the 'Building terrain' screen is displayed. It might take over 15 minutes. Once the main controls are displayed the world is not presented correctly and I would only see the moon or sun but controls 'W' 'A' etc doesn't move the character as the coordinates would not change. However I will be able to use the mouse to view the surroundings (refer to screenshot) After some further time, the world is displayed correctly and I will be able to progress navigating. However, I noticed that when trying to apply a fire charge on a TNT it either takes very long to light, get stuck after flashes or it doesn't light at all.