The weirdest bug - I can’t boil it down further to less lines of code because of reasons you’ll soon see.
Some other troubleshooting steps I’ve taken first:
- I’ve run the html and javascript through online validators, all seems to pass.
- I’ve hosted this through xampp / chrome locally and it loads up no problem, no errors in console.
- This bug patch (and the original project) runs fine in 2020.28110, and has for a long time.
Ok so my troubleshooting process has been to remove chunks of code until things work again - pretty straight forwards. I got to a point though where removing different functions would fix the issue.
Then as I slowed down and started removing smaller pieces, I noticed that even removing trivial lines, even lines like a javascript comment caused the web render top to start working again.
// returns a dictionary containing the absolute offset in x and y, of an html .
I then noticed that If I left that comment line in… and took out some other block of code that wasn’t even being used/referenced that looked like this:
var left2 = 0;
var right2 = 0;
var top2 = 0;
var bottom2 = 0;
This would also cause the web render to work.
This leads me to believe the problem is maybe related to how much overall text is in the webrender… something I thought we ran into quite some time ago and got patched, but alas maybe it’s different or more complicated than that.
For reference, here’s the older bug that came to mind:
So, the file I’m attaching while there’s a good chunk of code in the broken version, the difference between the broken and working version is literally a javascript comment that I took out. 
Hope this helps!
webRenderBug.3.toe (5.9 KB)