Jalview can get into a state where drag within window starts scrolling

Open a large alignment. Start drawing a selection group and drag right off the alignment panel so that the alignment scrolls while extending the selection group outline. Move left into the panel and right out of the panel several times while still dragging. Release the mouse in the window to finish the selection group. Click off the selected area and drag as if to create a new selection group: the alignment panel starts scrolling of its own accord. In 2.10.2 this may also throw an NPE (this is fixed in JAL-2665).