A very good friend who has significant experience in air refueling an HH-53C from a C-130 wondered if a contributing factor might have been sun angle at 1600 local. I looked up a sun angle calculator and took an easy out by using the data for LAX at that time of day, and the elevation angle is between 18 and 19 degrees. He may have a point, depending on how the join up was being run.
( and if the sun was out )