Hi,
There's a bug in the add/join shapes functionality. Sometimes the final shape produced by joining multiple pieces together is not necessarily the same as before joining operation. The produced shape is distorted.
Please refer to the following video for illustration of the issue.
https://www.youtube.com/watch?v=Lhi8gZCnZSM
I am also attaching an example file. Please not that the result produced are sometimes different if I restart the application and reopen the file.e
The shapes in the example file were produced by duplicating a square with rotation using the Cmd-J keyboard shortcut.
add_shapes_bug.afdesign