Q: After I completed my project on a symmetrical base I had to modify it again. I released the symmetry to allow the new data to be entered. As a result of the calculations I found it necessary to include some more symmetrical walls. So I reinstalled the symmetry. My problem is, all of the faces and other items seem to appear twice. Is this a program bug?

A: Sorry, no. If you decide to switch on symmetry again, the program has to make the room symmetrical again. This would be an easy algorithm for small rooms but difficult for big projects. Therefore the program will automatically create a symmetrical twin for every item in the project. This leads to full symmetry.

To figure out which faces and other objects already have existing parts on the other side of the symmetry axis is rather problematic. Until we found a way to reinstall symmetry more efficiently in most cases our recommendation would be:
Once symmetry is off - leave it off.