I have one which had some similar issues. I also replaced the main spring.
Here's what you need to really check. Do you get the issues on the first cylinder at range with a clean gun?
The metal used to make this guns is really sensitive to temperature. The metal expands rapidly with the heat of being fired.
The cylinder typically has pretty tight tolerances, which makes getting the rounds fully seated pretty hard. If a .22 round isn't seated completely, it will not often not go off.
I also have a theory that the expanding metal somehow binds up the action just enough to slow the hammer down a bit.
That all being said, H&R revolvers aren't super high quality. Mine is in pretty nice shape and it's a family heirloom, so I'll always keep it and shoot it occasionally. I have other experiments I want to do once .22 becomes more available. I think shooting .22 Long or .22 Short (instead of .22 Long Rifle) would lessen the pressure and heat and make it more reliable.
So that's my experience. Mine is really accurate, and it's fun to shoot.