That question is very popular & there’s actually a recent discussion regarding it! I have provided a link to the discussion below. It’s generally more effective to put all the pieces of one garment in one drawing space, they can be traced with the workpiece tool to produce the separate pattern pieces without trouble. Of course, you still can’t safely time-travel, (too likely to end up with infinite recursion,) but then it’s possible to try. (Be sure to try on a separate save file, lest you risk losing all your progress.)
Hi. Meanwhile I found the solution by myself. I’m programmer and when you think about it, it’s clear, that this is done because of endless loops. I opened the xml file with the editor now and copied the 3rd workpiece in front of the other two. The third one doesn’t use variables from the first ones, so there is no danger for a loop. That worked great thanks for your help.