EDITED BY MODERATOR: Moved to Bill of Materials space. Please post in the appropriate space when one exists. The API/Macros space is for if you are using the SOLIDWORKS API (Application Programmers Interface) or using/writing macros.
This is a known problem, new to SW 2019. It is fixed in SP3:
Drawings - Tables: Modifying column header (name) in the Bill of Materials (BOM) automatically adds slash ('/') before the header
Retrieving data ...