here is a picture of the channel see where it was riding on the bottom of the channel. It needs a stop plate at the back of the channel. look to the right there is nothing to stop it from coming out.
If I am looking at this photo correctly this is what I see. Is this correct? If so, based upon the grease marks, it looks like the bearing was pulled out from front. As the lift is raised, the bearing moves from the front toward the center of the lift. The grease marks inside the channel run the full length indicating it has been raised up to the top. The grease on the bottom of the channel indicate that it only been raised about 4/5's of max height.
What year is your lift? Mine is a 2011 and it appears the top channel is different.
Given what I see, anyone with any lift should check the channel.
Thank you for the information bubtrauma.