Fix the patterns in mirrored groups issue. Please refer to this post and my comment at the bottom. The work around suggested in this post is not sufficient for projects that have an angle, best I have been able to figure out in my testing. As this was a request years ago, I would suggest to the development team that this be considered a higher priority item to get fixed.
https://forums.autodesk.com/t5/revit-architecture-forum/help-mirrored-group-elements-do-not-retain-s...