Shift + left/right arrow keys acting weird in the timeline

up until today using shift + left/right arrow keys always placed the playhead in the timeline to either the start or the end of the animation. but suddenly (i dont know what happened) using that shortcut makes the playhead jump forward/backward exactly the length of my set frames per second in the output options manager… (for instance if i set 24 fps, the playhead jumps 24 frames instead jumping to the start/end of my timeline)… and i cannot undo this behaviour… any ideas?