I'm just guessing here as to what was going on. Normally resting the forearm on a rock, log, or anything hard will usually make your point of impact higher. Anther thing was your first shot was with a clean bore???
After your bore was fouled you next 2 shots
probably hit just under the target without cutting paper. Your next shots hit the bottom of the target in a decent group.
I would repeat this shoot but next time rest the forearm on something softer. Even a rolled up towel will suffice. I'd be willing to bet your first shot on a clean bore will go high and the rest will be lower.
Also be conscious as to how much compression you put on your load. Try to stay consistent.