Mirror Parts in Assembly

Hello,

I was using the Mirror function in my assembly, but I realized my mirrored assembly didn't match to the original assembly. For some reason, the mirrored assembly is tilted or on an angle compared to the plane or the original assembly.

Is this is a known issue with NX 9? Is there a way to fix this?

I have tried it in NX 10, but it doesn't seem any different. Any advice?

Thanks,

Jason Brehmer