Backstop does not correctly render web pages

Hi, we want to use BackstopJS to monitor design "crashes" on our WordPress site. For some reason Backstop differently render web page for reference and test cases ( different font size, also I noticed that sometimes images does not load at all). I set 1920x1080 screen size but looks like that reference and test rendering in different screen size. I tried also docker way to run Backstop but it has the same problem. I thought this problem related only to our site but when I tried to use google.com the same problem appeared. Do you have any idea what I'm doing wrong?

No source files or tests are named. Start by reproducing the mismatch with the stated 1920x1080 viewport on google.com and the WordPress site, comparing reference and test runs with and without Docker. Done means both runs use the same viewport and consistently load matching fonts and images.

Written by the indexing model from the issue text.