I have a similar issue with dogbone dressup. However, things are a little less deterministic in my case, it seems. Sometimes, changing stepdown after using DogboneDressup locks up FreeCAD, sometimes using the DogboneDressup path modifier at all with something else but the default tool locks up the program. I've looked into the Python script for Dogbone, but it was not very obvious to me what happens there. Is there any documentation regarding the Path toolbench and its code? So far, I have only found
https://wiki.freecadweb.org/Path_scripting, which doesnt cover very much.

- freecad_freeze1.png (225.97 KiB) Viewed 1624 times
By working around with using the default tool and job parameters at first and changing the tool and cutting depths etc. later, I could manage to get closer to my desired outcome, however changing parameters like stepdown freezes everything again.

- freecad_workaround_pre_freeze.png (192.14 KiB) Viewed 1624 times
If someone more competent than me could look into the issue and maybe even give some hints where to start with understanding the underlying code/FreeCAD framework, I'd be very glad.
OS: Ubuntu 20.04.2 LTS (XFCE/xubuntu)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.23756 (Git) AppImage
Build type: Release
Branch: master
Hash: 9c6e9184930a52b165a0b7274e3a45d1006bfe67
Python version: 3.8.6
Qt version: 5.12.5
Coin version: 4.0.0
OCC version: 7.4.0
Locale: German/Germany (de_DE)