Symptôm: One of the parts of the mold document can not be selected from the graphic area.
Possible cause: The graphic status of the part has been changed and it is no longer possible to select this part graphically.
Solution: Close TopSolid and modify the TopSolid shortcut by adding the option -d at the end of the Target field (see below):
After restarting TopSolid, the contextual command Restore picking... is available from the entity tree.
Select the part and run the Restore picking... contextual command.