Often, a replacement hand is made with extra material on its tip.
The hand almost always needs to have a little material filed off of it so that it will work with the ratchet teeth on the cylinder.
The fact that the hammer refuses to be moved much more than 1/16" when the hand is trying to engage the ratchet on a few chambers indicates that the new hand is trying to engage a new ratchet tooth but because it is too long, it is hitting the front of the ratchet rather than dropping down into the next tooth.
As several have said, it usually only takes a very little amount of material being removed to solve the problem.
The hand by the way is not hardened so a metal cutting file will rapidly cut away the end surface.
With this in mind, work slowly, removing just a little at a time. Then, try the hand by partially reassembling it with the hammer and gun.
If it works, you've done a good job.
If it doesn't, remove it and file just a little bit more. Then try it again.