When the command GROUP is used to group dimensions and texts, it creates leader lines which are invisible.
The leader line can be seen with the command SHOW_INV_GEO. By doing this, Drafting adds the info INVISIBLE to the leader lines of the groups.
The problem is when you want to clean a drawing of the invisible elements coming from other file format such as DWG: if the tip given in the Help > Program Ref. Guide > SHOW_INV_GEO:
SHOW_INV_GEO GLOBAL CONFIRM
DELETE SELECT GLOBAL INFOS 'INVISIBLE' CONFIRM END
is used, it deletes silently all the groups as well.
The Help should at least give a warning. The best would be to re-arrange something on Drafting to avoid this problem.