Combine fuselage with external box

Hello guys,

I am trying to combine-subtract the fuselage(solid body) of the part attached with an external box so that i can use it for a simulation.

When the body is at 0 degrees the combine-subtract command runs fine. Unfortunately the problem starts the moment i use the

move/copy body command. After i rotate the fuselage 40 degrees around the x-axis then i try to combine-subtract them and the combine fails

with an error message that it will create invalid geometry.

I cannot understand why the first combine succeeds and the second one fails.

Can you please help me out to understand what is happening..?

I have attached the part below..

Thank you in advance