Last two hunts with my dad have seen the same story:
Plane drops us off, we get gear stowed, and pull out our rifles to make sure that neither Alaska Airlines nor the trip on the bushplane banged the scopes around too much.
One trip we were at a lodge. The owner had a benchrest and a 100-yd target frame set up. My rifle was right where I left it, dad's was off by 4+ inches. (Wouldn't you know the grip on his stock broke on the benchrest while he corrected the zero. Glue to the rescue!)
The next trip we were at a remote cabin. I brought my $1.39 rangefinder (100-yd roll of dental floss), but dad had borrowed one of the laser jobs from a friend. We checked zero at 200 yards. My rifle put a round within 1 inch of where I wanted it. My kid brother nailed the bullseye. Dad didn't hit the paper. We moved the target to 100 yards and he re-zeroed from 5+ inches off. I should note that dad's rifle travelled in the same case as my brother's.
Anybody care to guess what's going on with Dad's Sako? It's got a beautiful Leupold scope, and he's carried it in the woods for years. A friend of his who'd been a sniper in the military once put three .308" bullets through the same .400" hole at 100 yards with it. But lately, it has to be re-zeroed to hunt. Once it's adjusted, he shoots good groups, so it's not the shooter. The rifle goes to and from the range in the same case without changing point of zero. We're confused.
It's gotten to the point that he packs a recoil pad with his hunting gear...