After changes in e4253633c9 the transition page content wasn't properly centered anymore in the single/double reading mode depending on the applied reader settings (scale type, stretch, reader width)
Depending on the screen size and e.g. the set "reader width" pages might not have filled out the full img elements size due to "object-fit contain".
This was caused due to the image wrappers flex container "align-items center" which slightly reduced the images width to some ".xy" number (e.g. instead of wrappers width 258px, the images were something like 257.83px)
