This looks similar on my machines. I found this workaround to kind of lessen the issue: I do NOT left click the thumbnail, but rather open it in a new tab. With most browser, this should just be a middle click on the image instead of a left click ... or its touchpad equivalent if you're on a laptop (2-finger tap on mine).
Yea, it comes at the cost of having to navigate through the image tabs (instead of just scrolling), but at least images are displayed correctly there - auto-resizing to window, zoom in/out available, scrollable when zoomed in ...
Maybe an important note (or not): Left clicking the image in a thread cycles between thumbnail and full-size mode. On my browser (firefox with a myriad of addons), the new image tab will always show the version of the image that was NOT shown in the thread when I middle clicked it - meaning, if I middle click on the thumbnail/preview in the thread, the full image will open in a new tab; if I accidentally already left clicked the thumbnail in the thread (hence cycled to full-image mode in the thread) and then middle click it, only the thumbnail will open in the new tab. I hope that makes sense, it becomes much clearer once you see it.