Thank you for reaching out on this GavrachBrown,
The PayPal App would sync both Invoices and Expenses from your PayPal account.
To work around that, you might like to consider turning off the transaction sync in the PayPal app and have PayPal connected as a bank feed or manually import CSV file via the banking tab so you can manually invoice only transactions.
Please note that bank feed connection will not work if you have multi-currency transactions in your PayPal account.
Hope this helps and please let us know if you have any questions.