I think I may have found a small bug, that I am able to reproduce.
I read many web archives inside EF, and trash them (using cmd-delete) moving to the next archive while keeping the focus in the viewer window, allowing easy scrolling there using the arrow keys.
I’ve noticed that if the next file is something that cannot be scrolled (in my case a .flv file set to open with VLC, thus displaying as a VLC icon), if I cmd-delete, then upon hitting the scrolling key I get a “bip”. If I cmd-ctrl-arrow switch to another record, I still get the “bip” and cannot scroll.
To get back the focus where I need it I need to click inside the viewer pane, or tab until I get the focus there.