Try to make sure that the Rotation of your Unioned Parts don't have any negative x, y or z values.
You can also try using the Command Bar CFrame script to move Parts or Unions by .0001 studs (yes, it CAN move in such small increments!) to make your Unions work.
Here is the script, put it in the Command Bar in Studio, select the Part, then make your value changes (CFrame.new (x,y,z)) or rotation changes (math.rad(x), math.rad(y), math.rad(z)) and hit Return:
for i = 1,#game.Selection:Get() do game.Selection:Get()[i].CFrame = game.Selection:Get()[i].CFrame * CFrame.new(0,0,0)* CFrame.Angles(math.rad(0), math.rad(0), math.rad(0)) end |