Hi Val, it sounds similar to the steps reported here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=2177.1

But yeah there was a bug in the previous Nov-21 beta with mirrored objects having a kind of messed up inside/outside directions. Later in that thread there is a patch attached to a post that you can download and apply to that previous beta to fix it up in that version.

But this should also be fixed in the new Jan-19 beta that was just released:
http://moi3d.com/forum/index.php?webtag=MOI&msg=2333.1

Can you repeat this problem in the new beta or is it fixed for you with this new beta release?

- Michael