I held the grip safety in and tightened the ransom rest onto the gun. It held the grip safety for the first shot but the shock of the recoil loosened the grip safety so it wouldn't fire the second shot.
Use a rubber band or equal - using a Ransom Rest is an art.
The inserts can't fit all the many varieties of grip safeties nor can the inserts fit all the varieties of ambi safety retainers perfectly. Consider doing a custom fit to your gun - though that's equally a real nuisance even pain.
Read the instructions many times.
The system needs settling shots - G. Gordon Liddy had a funny story about settling shots in his memoirs - really cranking down is not my own preferred technique.
For all I know your pistol may not settle - for sure a pistol that for one shot holds the grip safety in and for the next shot lets the grip safety move out that pistol is moving around - the rubber band can make the pistol shoot and for all I know may help hold the pistol still in the adapter but the history of movement may say something about how well the Ransom Rest will work for that pistol and load.
Some pistols with loose slides do as well hand held by a really hard holding sharp eyed shooter as they do in a Ransom Rest. I like mine more for qualifying rimfire ammunition than most anything else.
For bragging groups throwing the first shot away and then shooting five self-loaded may give a better bragging group
I have never had this issue but ow that I think about it, all my GS's have the bump on them so that probably helps. A few wraps with electrical tape wouls take care of it as well as the other solutions.