Karol
What you need to do is both tedious and pretty simple:
In your case, I’d want to see a line or two of test code that fails, along with the failure/error report it produces. I’d also like to the the HTML of the element that fails. If you can also add the HTML of the new element which you think causes the issue, that would be good too.
Like I aid, tedious. But not exactly difficult. Do that and we’ll be able to help (or ask more focused questions).
Grabbing screenshots of active HTML is best achieved using the DevTools.