We've been getting random sporadic duplicate orders since we switched to v1.5.6c earlier this year, not a lot, but enough to annoy our CSR. Here's our setup:

Zen Cart Version 1.5.6c
PHP Version 7.1.33
PayPal Payments Standard

I've made a point in not installing any mods which edit core files. Having said that, we do use third party mods but none which (to my understanding) should conflict with PayPal Payments Standard. Most are either admin-function- or price-discount-related.

The only thing in our error log is this:

[21-Nov-2019 15:08:46 America/New_York] PHP Fatal error:  Cannot declare class order, because the name is already in use in /home2/xxxxxx/xxxxxxxx/xxxxxxx/includes/classes/order.php on line 1156
Line 1156 in my includes/classes/order.php file is just a }.

Any ideas?

Thank you!