Just open the pan/crop window for the affected event, delete any keyframes you’ve added (so that you then have only 1 keyframe at the beginning of the event), then select that keyframe, right-click on the video in pan/crop and click “Restore”.
If would like to effect additional events with the same procedure. Copy the event you restore, then control click & paste onto your new events.
Now you don’t have to go and change every event on your timeline.