[Multisite] PNG overlay breaks on the second site

Plugin version: 2.2.3.1

The PNG overlay does does not work for the secondary site under multi-site system.

Check out the image here

In the example shown, the website is a multilingual news site, the english website can be reached through “/en”.

The PNG overlay works fine on the primary website. When an PNG overlay is used on the images of the english (secondary) website, it results in a broken link

What the plugin gives:
https://thejoban.com/en/wp-content/plugins/wonderm00ns-simple-facebook-open-graph-tags/fbimg.php?img=https%3A%2F%2Fthejoban.com%2Fen%2Fwp-content%2Fuploads%2Fsites%2F2%2F2018%2F02%2Ffcdeb15c2e9a4d66ac9f3db00d98242e_18.jpg

What it needs to be (removing the “/en” and “%2Fen”):
https://thejoban.com/wp-content/plugins/wonderm00ns-simple-facebook-open-graph-tags/fbimg.php?img=https%3A%2F%2Fthejoban.com%2Fwp-content%2Fuploads%2Fsites%2F2%2F2018%2F02%2Ffcdeb15c2e9a4d66ac9f3db00d98242e_18.jpg

I could add my own workaround and just remove the extras with PHP but I need to be sure that this is an actual bug and not some bad configuration on my side.