Wow, there sure seems to be some buggy behavior in there. I tried a coupe things and at first I thought the external cut i used to trim the truss diameter was causing issues, and it was, so I fixed that to not use any cuts on the outside. The first 2 mirrors worked fine, so I got the bottom 4, tried to mirror that and it bombed, with a couple features in the group failing. The pattern worked a little better, but still a few non-regenerated features.
What Pro/E SHOULD do is simply mirror the GEOMETRY, and not need all the baggage of copying all the internal sketches, etc.
Got a few tricks still. 