Error loading references list from Zotero.

Hi,

I love Bibbase, especially the latest theme, thanks for all your work on this.

I was hoping you could help with a recent - but increasingly frequent error. Occasionally when I load my publications page (https://pedrovale.bio.ed.ac.uk/publications) I get the following error message:

• Warning: file_get_contents(): SSL operation failed with code 1. OpenSSL Error messages: error:14090086:SSL routines:ssl3_get_server_certificate:certificate verify failed in eval() (line 1 of /disk/data/www/drupal7/modules/php/php.module(80) : eval()'d code).
• Warning: file_get_contents(): Failed to enable crypto in eval() (line 1 of /disk/data/www/drupal7/modules/php/php.module(80) : eval()'d code).
• Warning: file_get_contents(https://bibbase.org/show?bib=https%3A%2F%2Fapi.zotero.org%2Fusers%2F837863%2Fcollections%2FM9VMJBQG%2Fitems%3Fkey%3DII3rucWmEcbdlGBRNINIxNWX%26format%3Dbibtex%26limit%3D100&theme=mila&owner=lastname&hidemenu=true): failed to open stream: operation failed in eval() (line 1 of /disk/data/www/drupal7/modules/php/php.module(80) : eval()'d code).

I've wondered if this is an issue with my Zotero library, but I can't see what the issue might be. I've used Bibbase using the same Zotero library for a few years and it's always worked very well. 

Any help appreciated!

Pedro