For anyone else experiencing this problem, I will post my solution: The plugin makes a check to see if a view cart button already exists for a particular company before creating one. It does this by checking the meta_value of a paypal_wp_button_manager_viewcart_button_companyid entry in the postmeta table of the MYSQL database. For a reason that I have not yet been able to work out, when a paypal_wp_button_manager_viewcart_button_companyid entry is written to the table, a null value is being assigned to this meta_value, so that when the check is made the next time, it does not think that a view cart button has already been made, and generates another paypal_wp_button_manager_viewcart_button_companyid entry, also with a null meta_value entry. And so on…
On the instance of the paypal_wp_button_manager_viewcart_button_companyid with the lowest post_id, I changed the meta_value from null to 1 (the post_id of my company. If you have more than one company set up, you will need to enter the appropriate company post_id). Now the check mentioned above comes back positive, and I have since been able to create a new button/short code without an additional view cart button/short code also being generated.
You will need access to the database itself in order to effect this change.
