I wonder if these are the trials a friend (sadly now passed away) told me about some years ago.
During the trials he was "volunteered" as one of the Beverley rear crew for a demonstration drop over Salisbury plan in front of a load of Brass, some of them from NATO.
The load was an Austin Champ and a 25 Pdr Field Gun and Limber.
Due to time constraints on the DZ the take off process at base was a bit rushed and some of the load checks were done a little on the quick side.
Anyway the run into the DZ went OK and the load was pushed down the runners and went merrily out the back with no sign of a chute deployment. Apparently someone had forgotten to remove the pins from the chute packs!
When the dust had settled on the ground the poor old Austin Champ was no more than 18" tall and the 25 Pdr gun barrel was bent like a banana!
It was an expensive trial for the Champ fleet as on another occasions the locks on the pallet failed when the a/c rotated on takeoff and the whole think went out the back and bounced down the runway shedding bits as it went.