Thanks for writing back.
> As this is us a a custom coded WordPress website, I was told to be careful when updating plugins or the theme or WordPress for that matter in case it causes incompatibility issues.
- Yes, the recommended approach is to make a complete backup copy of the website, before proceeding with plugins, WordPress, and theme updates, in case of custom-coded websites (that is where fair amount of code customizations are involved).
> My initial guess was that perhaps something automatically updating and that’s why this issue occurred all of a sudden. Is that not what you think might have happened?
- Reviewing the website, it seems like the WordPress automatically updated, but the active theme 'Astra' and the plugins were not. This would explain the script errors since script libraries are jointly loaded and used by WordPress, themes, and plugins. This means that either all of them should be updated over time or none of them.
> Would you still recommend I update everything? I just don’t want plug-ins to fail and have inter plug-in compatibility issues.
- Yes, here are the steps that I'll recommend, to make sure that updates are safely applied, without affecting the actual website:
1). Make a complete backup copy of the website and download the clone:
Officially we use and recommend the following two plugins:
a). Duplicator – WordPress Migration Plugin
https://wordpress.org/plugins/duplicator/
b). All-in-One WP Migration
https://wordpress.org/plugins/all-in-one-wp-migration/
2). You can deploy this clone to any online or local host server.
3). Apply the updates on this clone, to see the effects and test if any compatibility issues arise.
4). If everything works normally, you can then apply the updates to the live/production website too.
I hope this helps and let me know how it goes.