WC API JSON error

Hi,

I have a self-hosted WP eshop http://www.mementerra.cz. I’m using the WC API to fetch eshop orders so that I can do other procedures with them (I’ve self-coded this in PHP). Everything’s been working just fine until 2 days ago (I guess when I updated the WC plugin), when it stopped working and upon debugging on localhost, I keep hitting this error.
http://prntscr.com/ngn425

The code I’m using to fetch the orders is here: https://prnt.sc/ngn6mw and here: https://prnt.sc/ngn6re

WP system status:
https://textuploader.com/1d5tm

Thank you so much,

Vít

The page I need help with: [log in to see the link]