Please update FreeCAD to latest stable (0.18.3)
Slackbuilds is offering an inferior version of Freecad (v0.17.13541)
Whereas the stable is currently at 0.18.3
as can be seen in https://github.com/FreeCAD/FreeCAD/releases/tag/0.18.3
Please consider updating. Thanks!
ref: https://gitlab.com/SlackBuilds.org/slackbuilds/tree/master/graphics/FreeCAD