Hi Vladimir, unfortunately that's probably difficult to fix.

Probably what's happening is your original arcs don't share an exact end point where they touch, there is an overlap of length about 0.0003 mm between their end points. During one of the steps for your save/reload/join/separate process the endpoints for the segments inside of a single curve are getting trued up so they are exactly meeting end-to-end but that small change is enough to disturb an arc that is such a small piece of a much larger radius.

I'd think you could solve it by getting the ends trued up exactly by moving the last 2 arcs away and then moving them back with end object snaps so they exactly touch end to end before doing your other operations on them.

That's what I did with the attached file, does it behave better for you?

- Michael