I’m also having an image alignment problem with a client site, except it is the same across at least three different browsers. I don’t remember having this prior to the last WP update (4.9.8). In fact all has worked great for months.
Specifically, my images were reduced & centered within a table row above pertinent data listed in rows below and have been this way for months. I simply used the image edit/center in the classic editor. Now every image done this way is left aligned, even though the “center” option is checked. What’s weird is you can view the page in page preview and it shows it to be centered.
Its when you view it live that is left aligns. The only change was the update and I have to say sounds like another bug with this update.