Receiving tiny payments in Paypal from unknown accounts

[inkandlead]

I have a relatively new store (launched in Nov 2020). It's a straight-forward e-commerce retail site. I had Paypal turned on since the beginning, and in January started receiving tiny payments ($2-$3, often less than $1) from names / email address I did not recognize, and did not match any customer contacts (my average transaction is $30). I received a few such payments a week from different accounts each time with a couple of repeats. I thought it was a Paypal issue, so I changed the email address associated with my Paypal account, but shortly after, received another payment of $0.20 from someone I have never done business with. 

I spoke with multiple people at Paypal, and the latest suggested that Shopify might be sending these payments as part of a rebate program, or that maybe it's an issue with the Shopify integration.

This is really strange, and I am not sure how to move forward. I've been refunding these unrecognized payments immediately after I receive them, but that doesn't seem like a solution. Paypal also suggested I block these senders, but that also seems unsustainable. I am wondering if anyone else has had this experience, what I should do about these payments, and / or prevent them from happening. 

Thanks!