I can only go on what’s been shown to me. You threw a lot of data in right from the start, and the problem is not obvious from any of that. I’m doing my best to help, on my own time. Please don’t be dismissive of the free efforts of strangers to help you solve your problems.
Now, the reason I said that is because your “wrapping the “default” layout with the default layout” comment led me to look more closely at the HTML you provided in your very first screen shot. There is a figure tag there, which has an a tag, which has an img tag. That img tag has a data-single-src attribute, which appears to be a complete HTML page, specifically the actual error page, instead of just some little bit of data. This appears to be the “wrapping” thing you’re talking about. So, my question is where that HTML is coming from, and specifically where the content of the data-single-src attribute is coming from. As far as I can tell, neither of these pieces of code have been shown so far.