I've moved your original post into this thread. In future, note that you can edit your subject line for the original post in a thread, and the entire subject for the thread will change to match.
Maybe someone else knows the answer with what you've given, but personally, I would need more information to try to reproduce the problem you're having.
Can you post a screenshot of the error you're getting from the Merge command, and perhaps post the IFC file for one of the windows that you're trying to use?
One of the forum moderators
AC 28 USA and earlier • macOS Sequoia 15.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB