Hey everyone! Hope I'm posting this in the right place - if not, please redirect me!

Let me start with a little background info. I do basic updates on the company website: editing/adding pages within existing formats and themes, and my account's permissions are limited. Due to circumstances we are currently without a web developer for support. I am encountering an error that is obstructing my ability to carry out the most basic of my tasks and can't really wait for a new developer to come along to fix it for me.

We're on version 8.2.1. Whenever I edit a content block on a page and go to save it, I get the attached error. This happens on every page of the website. The changes (obviously) don't get saved and I can't edit the page again.

I was wondering if there's anything I myself could possibly to do solve this issue - or if anyone here can even tell me what the issue is/in what direction to look for a possible solution/etc. Thanks in advance!!