Hi, I do not have any direct answer, hope below helps.
- I remember there is hints that sketcher tends to solve the geometry interactively when user move the edges with mouse.
- With constraints like angle, datum etc., where user input figures with huge difference, the geometry may 'flip' when there could be a number of solutions be solved to a problem. And this may leads to error when this is in contradiction to other constraints.
- I experience something similar when I try to do something on sketcher with python
- I was told to try other Sketcher Solver (tick Show 'Advance solver control' in preference...and find them in sketcher task panel) e.g. LevenbergMarquadt rather than DogLeg
- Or in my python script to change the parameter in more steps...
- @Chrisb has a tutorial on sketcher https://forum.freecadweb.org/viewtopic.php?f=36&t=30104
- @Chrisb, @abdullah and probably others help a lot on sketcher, and I remember they develop sketcher features - @abdullah even helps do some low-level C++ features for me to solve a few of my python sketcher::featurepython problems
- you may ping them, unfortunately @abdullah seem not around for almost 2 months, hope he is fine