Fatal error with substrate plugin; 500 error; admin panel inaccessible

Hello!

I am not a savvy WordPress user, but by the look of it, I need to get up to speed very fast. Three years ago I hired a web development team to build a WordPress-powered website to host my articles. They accommodated my host’s lack of SSH access by doing the development work (WP+Plugins) off-site on their own development server, before using SFTP to copy over the files.

It worked really well over the past three years, but several days ago I could no longer access my WP site nor its admin page. It gave the generic HTTP error 500 when trying to access the site or the admin panel. The host provided me with a quick analysis, that it seems to be due to the substrate plugin:

[25-Feb-2019 20:17:13 UTC] PHP Fatal error: ‘break’ not in the ‘loop’ or ‘switch’ context in /mnt/stor7-wc2-dfw1/538952/985776/www.mysitename.com/web/content/content/mu-plugins/substrate/modules/utilities-link.php on line 89

The host thinks it may be an issue with the substrate plugin and recommended me to reach out to the author.

I enlisted the original development team to troubleshoot it, but due to the lack of SSH, they are unable to assist.

Since I am now on my own (fortunately the website is not mission critical), it seems the only way is to mount the content locally with something like ExpanDrive.

If I do that and try to troubleshoot on my own with my limited WordPress knowledge (I used to be a Java/C# developer many years ago), would the ExpanDrive work like an emulator that comes with enough libraries for me to try to run the site locally (therefore not needing SSH or telnet)?

I think to replicate the error locally would be my first step, then I will learn how to remove plugins without the help of admin panel, as well as the possibility of updating WordPress + plugins to the latest version.

Am I on the right track on how to approach this problem?

Thanks!

Victor