I'm trying to figure out what would cause the floor to disappear so I have no suggestion there, but for the credits I would add debug messages to unlocking the door
if(GetLocalVarInt("IsDoorunLocked") == 1)
{
AddDebugMessage("IsDoorunLocked equals 1", true);
}
And then another just above the credits along the lines of
AddDebugMessage("Credits should start", true);
That way, you would be able to tell whether or not it gets to the credits, or if the problem is the variable itself.
Edit: Did you accidentally alter the .mat file selected for the floors? Or intentionally alter it? If you did that might be the cause of it, the floor more or less turns invisible while still having the collision and such but still looking proper in the editor, is that the problem you have?