Customers lose accees to courses when buying a new product

For some customers we use the “Update User Course Access Permissions” to give access to courses, but when these later purchase a product that’s not set up to give course access, they lose the previously assigned course access. Is this caused by this plugin, and if so, what can we do to prevent this from happening?

https://www.ads-software.com/plugins/woo-commerce-addon-for-wp-courseware/