Kerbal Space Program

There seems to be some issues with the plane hangar, there are a lot of white flickering squares at the bottom of it when in construction mode. Typically what you would see when two objects interfere with each other in games, maybe the ground is touching through the floor of the plane hangar?

There's also a bigger problem, that makes it impossible to attach parts to the plane. I was trying to build my first plane, but after connecting Mk1 fuel tanks to the Mk1 Probe, I couldn't attach the tail piece as it would be halfway through another object. After this it would also give me problems with other parts not wanting to attach any longer. Fuel tanks want to be placed halfway into other parts.
Engines doesn't want to be placed on wings at all.