@Gijs please watch the second video of my new post here Critical Rhino Bug: Chamfer/Connect + Join Corrupt Line Orientation
The problem is that some commands, such as ‘connect’ and ‘chamfer’, don’t affect the geometry if the distance is minimal (by not affect i mean they don’t extend and trim the lines to intersection as expected ). Meanwhile, the join command joins two lines that don’t touch each other by averaging the distance of the gap.
The loss of parallelism is an effect of the join operation in lines that do not touch