I thought it would be worthwhile digging this issue up again.
Because of the described unreliabilty of groups, we ended up burning a lot of time on it in the past.
Since then we are not copying or rotating groups anymore nor are we attaching walls to anything else.
This has solved the issues so far for us.
However do we still need to treat groups like ticking time bombs are are they save - 6 years later - now?
It would be great if autodesk could give me an update on this.