Doug,
if you were dropping the Muirhill it would have been a seven parachute set of 66's. Having dropped something similar it was not unknown for a rig with that number of main chutes to leave the a/c a little later than advertised. I was told that this was due to the large chutes fighting for position in a fairly restricted area. They usually got things sorted out BEFORE the de-reefing mechanism kicked in. In your case it sounds almost like they were starting to de-reef with the load still firmly in place !