The cracking could be stuff breaking up/ moving out of the joint that was causing the restriction. With new range there is new responsibility.
You may be accessing muscles/tendons/ligaments that have not been accessed before, moving stretching these in new ways, challenging positions, resetting positions etc. may move moves and tissue in new ways and to new end ranges.
Pain is your body’s way of letting you know something is wrong. So if there is pain you would want to re look at what you are doing. Soreness may be part of where you are at in working to improve the mobility in that area, tissue, muscle etc.