The down stop (located at the handle) has become rounded off due to wear. This stop should be re-worked or replaced. You may be able to file it back to original shape which is more than 90 degrees. Most all SH ships have this problem after about 10 years in service.. Look at the rounded off corner, it should be about 100 degrees. Its probably made of 1/8” hard plastic. I have “adjusted” this stop with a triangle file and made it a rather sharp 100 degrees again. Badly rounded stops need to be replaced which I have done by making a new one out of 1/8” aluminum bar. Check the “over-center mechanism after you adjust the stop by trying to collapsed the gear. This is done with the ship in its trailer saddle, then shoving forward on the drag links at the rear. It should not move more than about an inch, then snap back again into overcenter position. Adjust this by making the down motion longer (half turn) at a time at the most convient rod-end fitting.
Hope this helps,
JJ