Tony,
We have updated to Core: 5.2.5 and PayPal: 5.2.4. We are still having issues with module.
Currently our site is only on HTTPS and the redirect URL on the Paypal Module settings page doesn't accept HTTPS it only takes HTTP.
Because of which Paypal return's Redirect URL doesn't match error. Created a bug request for the same. Hoping you could shed more details on the same as well.
https://bt.x-cart.com/view.php?id=44769
-Raghu