If the window is taller than history the history is never loaded.
Per title.
In deeper detail: if the window is resized when fractal is first re-opened and history hasn't loaded/refreshed, and the new window size is taller than the first history load (however many lines the default is), then it becomes impossible to trigger a further history fetch via scrolling (eg, mousewheel).
This is very easily demonstrated on a vertical monitor by re-opening fractal then switching it to maximised before fully loaded.